as above can i use a 9 speed road cassette on a 9 speed mountain bike hub whilst using trigger pods?

Yes (So long as you stick with SRAM or Shimano)

As Clubber says, just make sure it’s not a Campag one!

yep, it works fine.

I have a 9-speed ultegra cassette on an XT hub and it works a treat.

The world will end.

It’ll be fine. Go to any DH race and you’ll see hundreds!

Actually, to be pendantic, the real problem is will it work with an MTB mech? The answer is yes, but not properly. Road mechs swing in a different arc to accomodate smaller closer ratio blocks. Hence why new saint mechs let you change this, and DHers tend to run shimano road mechs (and cos they have shorter cages).

You need a 9sp mech though, although a 10sp will work with some washers to space the cage.

Having said that, you may be able to set a mtb mech up fine. Indeed i’ve had a med cage x7, ultrega 12-25 block and pro2 hub working perfectly on my socom for 18 months now.

yep shimano 105 short cage works much better

Yep Dura-ace 12-27 on a Mavic SLR hub on my hardtail works a treat (XTR mech)

I run a Medium Xtr mech with a dura ace 12-15 on a Crossmax SL with no probs at all.