Then I recommend going a full inch module shorter(in your case a 27" mod)and then you can add your string loop to get your 27 1/2.

Don't get me wrong using the string and cable are a great way to make fine adustments but often people will twist this untwist that and then they can't figure out why thier bow lost poundage or won't shoot advertised speeds...Or whatever...

If you're talking tweaking a little here or there I'm sure it won't be off too much but make sure you check your poundage after you're done. I don't know Diamonds bows all that well, these changes may not effect their bows the same way as a BowTech...