Not entirely disappointed by the lack of squirming, Optimus simply shifted his own position slightly. He own knees further apart, grip on the end of the energon line tightening...

Forcing Megatron up the slightest bit more and realigning his legs, properly utilizing the full length of the spreader bar, widening the gap between his thighs and increasing the exposed surface area around his aft and elsewhere.

Then, he resumed swinging, palm striking with a far more satisfying crash and flush of friction-heat.

He'd draw sparks yet.