Ball Flattening - Superior Spin Mechanism than String Snapback?

I strung up my shortened (26.6") Steam 96 with a really stiff and low-powered stringbed. 61 lbs, Ashaway kevlar 16 / Prince nylon 15L.
The Steam is a great platform frame because it's really lihgtweight with no extra mass anywhere on the frame, so I can concentrate mass in my favorite spots and test weighting concepts.

At first it was too low powered when the SW was in 340s, but really spinny. So I upped the SW to high 350s. Still really spinny, if not moreso, but still a little low-powered.
So I beefed up the SW to the low 370s. Due the shortened length, the effective mass in the head was now equivalent to that of a standard length frame with 390 SW.

Now the power level was medium, with the massive hitting weight offsetting the low-powered stringbed. After an hour of hitting or so, I noticed that the mainstrings were no longer sliding as much - still snapping back to center, but hardly moving at all. The spin level was still excellent, but now the volleys suddenly got a lot more precise than during the first hour. I suspect that most of the spinniness is now coming from the unusually high degree of ball-flattening (i.e., extra pancaking), but I'm not sure (it could still be snapback contributing). This setup seems to give me superior control compared to stringbeds that slide a lot laterally. The plowthrough is off the charts, which I really like on returns and groundstrokes, feel is grippy yet precise with targeting. Feels a little like when you hit a ping pong ball with a foam-rubber-surfaced paddle.

I think next I'll try the same thing on a denser pattern frame, which should test whether ball flattening or residual snapback is the main contributor to spin in my Steam.

P.S. a 3.0 lady who was playing on my court before I got there got intrigued by the 6 layers of lead tape from 1-to-3 and 9-to-11 (35g added to upper hoop). She asked to try it. She was mesmerized by the feel and couldn't put it down. I don't think she'd ever felt a racquet plow through the ball like that before.
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trav, this was what I remember from the last of our conversations from around 2006. I was using a scale and pulling a tennis ball across various types of stringbeds with different amounts of weight on top of the ball, trying to get a force/friction curve. I remember that poly was the lowest friction stringbed at low pressures, but ramped up more quickly as pressures increased than the other materials. The early high speed photographic evidence was that every string was "rough" enough to fully engage the ball when it was at maximum compression. I remember speculating that as a ball is compressed, the effective radius decreases and so any stringbed movement in the vertical direction acted to create a greater rotational speed than with a tennis ball at its uncompressed diameter. As the ball rebounded, I thought it might be possible that the force/friction curve of poly would allow the ball to disengage from the strings while still compressed to a smaller diameter, essentially retaining more of the angular momentum built up against the smaller, flattened diameter.

I don't know if that was ever proven not to be the case, or if high speed photographic evidence can't discern something that probably happens in a few ten-thousandths of a second, if it happens at all.
Ball flattening generally also means less power so you can swing harder and still control the ball. Swinging harder also means more spin potential. I played with an Yonex RDX 500 many years ago with pro blend at 60lbs. It was quite board like, but I could wail on the ball and got excellent spin on my groundies. That tension was too much for my wrist along with how hard I was hitting so I abandoned that setup. It was very good while it lasted though. I think the other thing that got me was I liked feeling the flex of the frame with that setup, but you could really only feel it when hitting hard, so it encouraged me a little too much. Now I hit with really flexible frames and looser strings so I don't have to hit as hard to get that nice flexy feel.
I think the debate when the Steam was introduced (and yours truly was invited by Wilson to try it out at a local country club demo session) was whether there was sufficient dwell time for the string snapback to spin the ball on its way out, or was the ball long gone by the time snapback happened.

But I think the Steam with its open pattern was a flash in the pan and is long gone, like most other racket gimmicks. I remember though that the measurements that were taken during the session showed my TS to increase by 200 rpm with the Steam compared to a reference racket, and the launch angle was noticeably higher.