So i ended up going with a "normal" mounting set up on my sliders/steps. If anyone else has a IFS 100 series then this might be of help.
First i made the stirrups. 6x75mm flat barstock, and since i don't have access to a decent HD press i decided to cut and weld the components. There's only enough room for two stirrups on my chassis as the fore and aft mounting points don't really lend itself to using stirrups all the way along. At the front most and rearmost mounts i've tied into the body mounts.
After i cut the barstock i first ran a root pass, then a cover pass with the TIG. All welding on this project has been done with TIG, it's definately my favourite welding process now!
Root pass
Cap pass.
Internal fillet
Stirrups finished, and the plates for the body mounts cut and ready for drilling/tacking
Stirrups are fastened with 2 x M10 8.8 bolts each and the body mounts will be fastened with M10 SHCS.
Trial fitting of the body mounts and drilling to suit