I agree, reinforcing the tips is just part of the equation. The underside of the tip is another part - many of the old bows have grooves that are filed into the glass and a non- stretch string might cause problems in that area as well. I suppose you could add an underlayment of material to go over those. But as mentioned, the glass itself and the glues used to bond it to the core are simply different today than they were back then.
I guess the way I look at it is that sure, I give up a little bit of performance by shooting an old bow. But heck, we all gave up lots of performance when we decided to leave the wheels off the end of our limbs!
The old bows can still do a mighty fine job as is. Fast flight is not required to shoot a deer. (Or a hog, elk, bear, or whatever) They've been dying for many years from arrows propelled by non-fast flight strings.
I have plenty of fast flight capable bows that I can go to when and if I am in the least concerned about maxing out performance.