Jon: in terms of discrete filters (00 vs 0 vs 1) it makes sense. In terms of dichroic filters, I'm not convinced it will work due to the mechanics of the filtering but I'll certainly give it a try.

Marco: indeed, I have a number of Ilford RC prints with lively highlight detail and in comparing them with my Kentmere FB prints thought maybe it was a brand issue. I can check that though because I have plenty of Kentmere RC (ignored up 'til now except to check it's speed against the FB) and a couple sheets of Ilford FB though that's warmtone.

I'll give the preflashing a shot... do you preflash white? filtered? Seems to me (totally guessing here) it might be useful to preflash magenta to get an upswept curve: high contrast will register immediately in the highlights but the lower contrast won't have any effect until perhaps VI.