Ah, my bad. In that case I would go 12str, 19dex. That 1pt less damage won't be a huge loss. However, (and this is just how I prefer to do things) I would still go 18 dex and use the 3 build points elsewhere. You'll still end up with a dex high enough to hit everything reliably. With multiclasses like this, I think you get more bang for your buck when you spend build points on the 1:1 stat increases than the 3:1 stat increase. If you end up with an odd dex at cap you can always drop the rgr dexIII enhancement and use those 6 AP elsewhere to help compensate.