: . . . . how do you
: keep from 'modifying' that nicely aligned bow and
: stern form from it's current vertical alignment?

Proceed with patience, work both sides at the same time, use a heat gun. I tack the sheer strips onto both sides in the middle, then start cranking in the upsweeps a little at a time swapping side to side, using clamps to hold the positions, usually spring clamps. I may take a couple days to get just these two strips in place, and it can feel like I'm mired until I remind myself that these are really important "cornerstone" pieces that "set the standard", and all others will go in easily in comparison.

Patience! It's possible to crank in all you dare and it still isn't enough. Clamp it all off and come back the next day, and you'll find that the wood has "gotten used to" its new shape, and now you can start cranking in more from there. Use a heat gun. Having both sides doing the same thing at the same time will keep stress off the end forms -- and you.

Yes, I'm a heat gun believer; I fought my share of recalcitrant strips the old fashioned way and it was neither relaxing nor fun. The heat gun has made it a very enjoyable process.