Thanks for the reply, I suppose the best thing to do is remove the feet just above the ankle. its kind of a shame, as the feet are really nicely (re-)modeled.
Oh, and yes, i did just vanish the feet in OS, but I don't yet know how to create a slider equipped body mesh like the skyrim/fo4 one with no feet.
I think I should continue experimenting,
1. mask the foot on the reference shape with the mask vertices tool
2. Brush -> invert mask
3. Sliders -> new zap slider
4. Select the new slider in the slider list (the pencil icon)
5. Sliders -> Properties
6. Set Default to 100 and check hidden
The feet are now zapped away when building the outfit in bodyslide.