I was thinking a board wider than the footboard - you could recess the castors via the bottom on the outside edges, and then rout out a centre area on the top that the pedal board could sit in. Keep it as close to the floor as possible
Sorry Phil, you use the same (or very similar) avatar to Glenn and I'm an addled old fart. Think I'll try the slider route first on the basis that it's the easiest and if it a no-go the regret spend is low.
Tim H. 1986 4/4 VVTi Sport, 2002 LR Defender, 2022 Mini Cooper SE