I've found only vague references to doing this (https://www.seabios.org/Build_overview#Build_as_a_UEFI_Compatibility_Support_Module_.28CSM.29), and no real guides / examples. 

Before I go on a wild goose chase, has anyone tried this before?

I've tried the other way around, loading DUET from SeaBIOS, but all I get is a brief message that's too short to read properly (but it looks like it's loading memory locations, didn't see any errors), then I land back at SeaBIOS.

Any pointers would be appreciated!

Cheers,

R