I have a couple of K90's and KPS88's laying around the house. In fact, the KPS is my oldest son's main stick. I hit with these probably a bit more often than I should, since my primary racquet is a Yonex but there is just something undefinably and uniquely satisfying about hitting a classic racquet in the prostaff lineage. I can suffer from some elbow tenderness on occasion, but I attribute this mostly to poor string selection or playing a poly way past its prime. I'll echo furyoku in recommending a soft string in these racquets. I have no problems hitting with either, although there was some initial general muscle soreness when first wielding the KPS. That passed fairly quickly.
I do subscribe to the hypothesis that heavier racquets deal better with absorbing shock. However, as Ralph states, these are also very stiff racquets, which conversely, can be rather effective transmitters of vibrations to your arm upon mishitting the ball.
Consequently, I would heartily endorse either the K90 or KPS88 if you both:
(1) can consistently hit a clean ball with a mid-size frame, and (2) use a relatively soft string setup. Otherwise, you may find that either racquet only exacerbates your TE.
For the chronic TE sufferer, in search of a comfortable, arm friendly racquet, I wouldn't recommend either the K90 or the KPS. There are much better selections out there. To the OP, you don't seem to place yourself in this category and, having demoed both racquets, seem to know what you want. They're fantastic sticks; you couldn't go wrong with either one. Good luck!
