Hey Alex,
maybe it didn't become clear that I'm the proud owner of several bikes - four to be precise.
And one of them is a road racing bike which I'll use for the qualifications and PBP. It served well last time. As far as I know the regulations do not exclude mountainbikes as such, apart from the fact that if I were to use a mountainbike I would use different tires, and most probably also mount a larger front chainring, as I had done for Trondheim-Oslo (550km) before I had the road bike...