Some guidelines suggest the use of use small caps for abbreviations. I have an issue with the following one: iTRAQ. Here are some guidelines on mixed small-upper case abbreviations. I do want to keep the small-caps version visually as close as possible to the standard one.
iTRAQ, i\textsc{traq}, and i\kern.07em\textsc{traq} look like this with the font charter:

The i in the two capitalized versions is larger than the small-caps afterwards and also TRAQ is lighter than the other text. Is there a good general solution for mixed-case abbreviations?
Update 1. Charter does not use real small caps, but scales the font, that's why TRAQ is so light. With kpfonts, which has true small caps, it looks slightly better, but still strange as the i is larger than the caps:

Update 2. Using Barbara Beeton's/tugboat's solution, I am happy with the result (second variant in the image):

Using small in normalsize environment, etc., to have fake (or true?) small-caps produces an results which is, for my eyes, visually appealing. The abbreviations are slightly lighter than true small-caps, but I can life with that for the benefit of having an universal solution.

iis an affectation, unless this is a trademark. – Dan Dec 08 '13 at 04:17\SMC(accessed by a derivative command\acro) to set caps one size smaller (but still using caps). the code is fairly involved, but we like the results. see the fileltugboat.cls; it is included in a full tex live installation, or can be found on ctan. – barbara beeton Dec 08 '13 at 15:51