I would suggest rearranging the shadows on letters that would make another letter if a part fell away. With imperfect vision and/or increased contrast, "E" becomes "F." and "L" becomes "I." The tail of "R" isn't quite shaped like punctuation but still seems a bit like a lost object lurking under a "P" all the same. Even if confusion is unlikely in practice, the differentiation will add more visual interest.

If you are attempting to produce a digital font version, as opposed to an eps format which allows gradual shading, check the discussions of the problems in in making a digital font of Roger Excoffon's Calypso type using a dot size variation. For example http://typophile.com/node/102099
Don

Pretty cool!
My only complaint is that the straight-to-curve joins (like in the "U") are ungainly (possibly because they're too geometric).

hhp