Not sure how that would affect the antiskating to much. I use very little antiskating on am SME V arm with the Benz LP-S. No problems using either speed on my setup.
Magnepan Unitrac I and Denon 103D(very low effective mass and high compliance). No problems here either, and I pay a great deal of attention to sound stage/imaging. It could be that your arm is more resistant to lateral displacement, than your cartridge's compliance, at the higher speed. Does your cantilever skew to the inside at all, at 45rpm?
At those speeds and deeper cuts, anti-skate keeps the stylus and arm in check, otherwise its digging into the record not seeking out the best groove information. Also the record at that speed could be off center enough to effect the sound...try some other discs. Would recomend Reference Recordings Symphony Fantastique by Berlioz.
The linear groove velocity of a 12 inch LP is about 2 1/2 time faster at the beginning of the side than at the end. If the anti skate was that dependent on speed you would need to slowly change it as the record plays.
A 33 1/3 LP at the beginning of the side has about the same linear groove velocity of a 12 inch 45 LP an inch in from the beginning. If you hear this effect because of antiskating in the middle of the 45 you should also hear it at the beginning of the 33.
I think something else is going on.
Your experience makes sense, both in theory and from my own.
RIDING ON A BEAM OF SOUND
From the stylus's POV, a higher groove velocity is no different than an increase in transient velocity. If we sit inside the stylus and look outward, we cannot tell whether any particular curve we're being asked to negotiate is a gradual curve moving past us at high speed or a sharp curve moving past us at low speed. The relative effect on us is the same: we're being displaced a certain distance over a certain time span.
A fast transient is harder for our stylus to track accurately than a slow transient. By analogy, consider a car moving over a bumpy road. A car moving at 45 mph will be more likely to lose adhesion than one moving at 33mph.
To the extent any lateral bias ("skating force") exists, our stylus will require more anti-bias ("anti-skating") to track fast transients accurately compared to slow transients. Therefore, higher groove velocities will tend to require higher anti-skating compensation.
Before my own cartridges relax enough to let me use zero A/S on all records, they go through a phase where I need TINY but VARYING amounts of A/S to track a FEW challenging passages. During this phase, the precise amount of A/S needed varies by LP and even by individual track. (In theory, it actually varies by individual transient.) The last passages to need a trace of A/S are very dynamic transients moving at 45rpm.
The above is true independent of whether or not a higher groove velocity increases skating force, which is a matter of debate between theoretical types.
The linear groove velocity of a 12 inch LP is about 2 1/2 time faster at the beginning of the side than at the end. If the anti skate was that dependent on speed you would need to slowly change it as the record plays.Quite correct, and your conclusion from that fact is consistent with my experience. Several fine tonearms, including mine, vary the amount of A/S they apply depending on the position of the arm relative to the record center.