Yes running them in practice is fine. pretty much the only tyre used at the oople race (dry) were 8175 ribs, more of a mixture at the 'dirty weekend' (damp) with a few drivers on suburbs - very little in it and no real decision as to which was better! So 8175 ribs and Holeshot rears and you'll be good to go
Few more entries and even the weather is slightly improving!
http://www.xcweather.co.uk/forecast/s81_8eu