Compiling HI-SPEED IMP on Amstrad NC with ZCN

[simulant]

Hi does anyone know how to create an overlay correctly for the NC100/NC200 in order to compile HighSpeed IMP so we can use this awesome CP/M terminal program in ZCN?

Here is the High Speed IMP source and sample overlays if anyone knows what needs editing so we can have it optimised for NCs:
http://planemo.org/retro/updated-imp-v2-46-high-speed/

qTerm is ok but doesn't support ansi extended character set. Not sure if IMP does either but it would be nice to try it and have a good alternative terminal program in ZCN - I know IMP used to be a very popular CP/M terminal choice...