hey - thanks jay - really appreciate your help - it's always good to find out it's maya that's having the problem... and not you!

render layers are new to me so i'll have a play and will keep your advice in mind.

in the meantime here's a little tutorial for breaking subsurface scattering into layers that may be worth a read.

https://www.nickbartone.com/docs/subs...rsTutorial.pdf