Ian, I tried your test in layered selections as you mentioned in split mode with variation 4 arranger style..and no real noticeable drop out..

I then tried the real torture test..piano mode with stereo strings layered with stereo strings and piano with full keyboard recognition..sustaining with repeated 10 note chords..after the 3rd or 4th strike ..yes ..drop out was evident..but in a way you could live with..the drop outs were the added stereo strings..the arranger play had no evident drop outs..This is where Roland shines with the priority allocation to most important parts...

No one in their right mind would play as above ..even with 256 poly..

My biggest nightmare (polyphony wise) was the night I used my new PSR320..trying to play over sequences...It was only 32 voice..and the way the Yamaha worked....when it reached it's limit..it shut down..no sound for several seconds...

Even my 28 (maybe 24 voice) voice E-66 never failed to keep the music going when playing over a seq..Allocation is the answer...