In both the Roman and the Italic:
– The descenders should be shorter than the ascenders.
– The "j" is too timid.

hhp

really? Most of the fonts I’ve looked at have the same length ascenders and descenders... && what do you mean the ‘j’ is too timid? I didn’t really want to put a huge swash on it

Actually most text fonts (and certainly the good ones) allocate more of the vertical space to the ascenders than the descenders. This is mostly because of letter frequency. What fonts have you been looking at?

By "too timid" I meant that the terminal of the descender could do a lot more than merely taper. It doesn't have to be huge though.

hhp

Hmm. Apparently some fonts have the same height for ascenders and descenders (like Minion or Proforma), but others have the ascenders longer like you said. I made the ascenders taller and the descenders shorter slightly but I think it looks a bit worse now, especially next to the capital letters and the ‘t’

And for the ‘j’, how does this look?

But it would be inconsistent with the roman ‘j’, as well as the capital form

BTW I made the capital Italics too:

Actually taking off the extension on the ascenders, they are still 10.4% longer than the descenders (5.4% with the head-serif overshoot taken off) is that enough?

Even deducting the head-serif overshoot, Minion's ascenders are at least 10% longer than its descenders. In Proforma it seems to be less than 5%, but it's there.

It's hard to nail down how much is enough, because it's not an exact science, and it depends on a number of things. But as a rule the more a font is serious about being read versus looking pretty, the greater the difference should be (up to some limit). I myself prefer ~20%.

Here's my personal guideline of good descender length for a serious text face: when the "g" –the most vertically "needy" descending letter– starts looking a bit too cramped, you're there. Because that's a good manifestation of the necessary balance of compromises.

hhp

I did as you said and made the descenders so that the ascenders are 16% taller (more room for accents, I suppose) The ‘p’ still does look a bit goofy sometimes though

Here’s a comparison to Minion Pro and Le Monde Journal scaled to the same x-heights

And the test passage

Italics

To me, looks more texty now.

The "g" could appear a little less small by having a larger top, flattening the bottom a bit.

BTW I'd missed this before:

it would be inconsistent with the roman ‘j’, as well as the capital form

Yes, make the Roman one less timid too.
But the capital is a different story, because it plays a greater role in display than text.

hhp

idk. I prefer tapered ‘j’s because they look more graceful to me and the blob on the end is either too distracting or awkwardly tiny. I think you can get away with blobbing the terminal more in the italic since it’s more calligraphic and the stress is more diagonal, but not as much in the roman