You're doing well so far.

t: It would be helpful for the crossbar to be at the x-height and extend right a little longer.

f: It is not too unusual for the crossbar to be lower than the x-height, nor too unusual for the ascender to be shorter than the others, but both at the same time gives the impression that the whole f has been scaled down to a smaller type size.

Italic h/k: The first leg is bent inward and the second leg straight. I see that you may intend to relate it to the Javanese this way, but this is strange and distracting for Latin reading. Normal italics have the first leg straight (because in handwriting it is where the pen sharply returns upward), and if there is a bend it is on the last leg. (But l is good and its difference from i is smart.)

Italic v/w/x: Not enough slant. Consider adding something interesting to the ends of the downstroke of italic x.
Italic z: Maybe too much slant. Consider a reversed stress similar to 2/5/7.

All s/S curves are going to need some fine-tuning. I can tell from your finished g that you'll get there on your own.

Thank you, yes to all that feedback. Working on it.

But honestly, I have no idea how to fine-tune the s/S. The terminals in particular really confuses me. It's like deleting the spur from a serif font, which make the terminals too hairline. The only similar reference I have is Sakkal Majalla, where the terminals are flat and slightly thicken. Any ideas?

In a contrasted of “stressed” sans, to balance |S| and |s|, one can’t simply use the shape of a serif |S| and remove the serifs (a textbook example of this mistake is Bodoni Sans http://www.myfonts.com/fonts/greyscale-type/bodoni-sans/ in which an otherwise perfectly good typeface is ruined by a backward leaning |S|).
As for terminals, they usually have the same shape of the ones on |C|c|, either thickened (example: http://www.myfonts.com/fonts/urw/britannic/) or tapered (example: http://www.myfonts.com/fonts/castletype/carisma/). However, the thickening can be very subtle (examples: http://www.myfonts.com/fonts/linotype/peignot/ http://www.myfonts.com/fonts/reserves/vanitas/).
In your case, though, I think the problem isn’t much with terminals, but more on the bottom counter, which looks somewhat “weak” compared to the upper one.

Thanks for the links, riccard0,

-S/s Like this I guess? Not confident with the S
-ligatures
-just personal, gaelic variants:)

Thoughts?

Apologies, that's the old s. Here is the edited s, which diverge from the arlier C and Gs. Is it ok for them to be dissimilar?

You have many different terminals here (|C|S|c|). Perhaps finding some consistency could be beneficial.
I also think you could open a bit the bottom counter of |S|.
As for ligatures, given the short hook of your |f|, I think a non-looping design could serve you better.

Go back to the first S. The terminal on capital C/G/S is very nice and helps keep the font from being plain. My mention of S/s was mostly about close-up smoothing of the curves in the middle, which is a challenge every time.

Ok thanks, reverted the terminals back to the old.

About the ligatures, is it necessary then for this font to have ligatures, since the hook is short? Perhaps only ff with connected crossbars is necessary. Other similar fonts has slightly rounded hook, prompting the nedd for ligatures, while this is flat.

If there isn't a problem of legibility or aesthetics, there isn't a need for ligatures.

The italic ascenders may call for an italic fl (and if you want to be very complete, fb, fh, fk). Other ligatures are clearly unnecessary.

Agreed, the ligatures in italic is standard, but otherwise it's discretionary. Thank you very much for the advice.

The other thing I'd like to ask is the harmony between the latin and javanese. I absolutely love the Javanese, I think it's perfect. Looking it side by side with latin though, I think its a bit crowded and heavier. Should this be addressed, or is it still tolerable due to difference in writing system? I tried looking samples of roman/indic font harmony in Thai fonts, but Javanese is very particular. The characters are inherently heavier I guess

I don't think that the Javanese looks darker, rather more contrasted (and obviously more "blocky").
Overall, to me it looks more "didone"/Melior than its Latin counterpart.

Once you are satisfied with the forms, you will have to work on letter spacing, and over all I think it can be made rather tighter, which will eliminate the difference you are concerned about, to the extent that the remaining difference in look can only be expected. I don't know anything about Javanese, but I assume that when the two scripts are set together, the stroke weights will be the same, with the Latin body larger than that of the Javanese because it doesn't need so much space above and below.

@riccardo I did thought to make the latin more didot, but then I'd prefer Aturra to be more of a body-type. I planned to do didot for my other display-type Javanese: https://www.behance.net/gallery/18447475/Javanese-font-Ngrawit

@cerulean yeah, I haven't touch the kerning whatsoever. I'll get to it soon.
The stroke weight is almost same when the characters are put side by side, but because the shape of Javanese is inherently blocky and didot-ish it look heavier in long texts.

Still need refinements, but is the general spacing adequate?

here's how paragraphs in English, Javanese, and Indonesian. (sorry for the large images)

Looks good!

Thanks cerulean! (sorry for the long reply)

Now I'm experimenting on a light variation and also Greek character expansion. Thoughts?

https://www.behance.net/wip/1065029