Hi,

I’ve two Niner carbon forks, one with a standard steerer and one with a tapered one. Would a Niner forks be any use on the Solaris? Which version fork would I be best off fitting?

If you scroll down on here: http://cotic.cc/tag/Solaris

There are some Niner forks fitted to a Solaris so they certainly work.

Take your pick both will fit with the right headset. (bottom cup)
also depends on how the steer is and how many spacers you use.

If given the option I would go tapered.

I’ve just built a Stanton Sherpa 29 with a tapered bolt through rigid fork designed to emulate(?) a 100mm suspension forks.

Works for me.

Are the Niner forks not a little short, i.e. 470mm AtoC?

From the Cotic site:
Minimum 80mm travel forks or 470mm rigids. Handles great with 100mm sus forks, strong enough for up to 120mm travel.