I probably would allow the partial profile designs to have larger standard errors, just like interactions and alternative specific designs. My reasoning would be a bit different, though. Whenever we've compared partial profile to full profile stimuli, we lose something in terms of statistical precision (i.e. the partial profile models have about twice the amount of statistical error that full profile models have). Counteracting that, however, is the fact that partial profile models have much less response error than do full profile models (it varies a bit from study to study, but on average, partial profile designs produce only about a quarter as much response error as full profile designs). So in terms of net error, partial profile designs are giving you better efficiency than you might think if you just looked at statistical precision (standard errors).