For H&H whats sounds like what you,ve done
250 2strokes are the ideal weapon! plenty of grunt and lightweight!
A re-packed silencer will last a good while and 2 strokes are generally not as loud as 4 strokes
As for tyres 99% of clubs running Hare&Hound events let you run mx tyres so no probs there
An 18" rear wheel is a big advantage as the tyre choice is a lot greater + the chance of a pinch flat is a lot less likely aswell due to the bigger wall on the tyre!
Gearing is more of a personal thing mate i find it alot more forgiving on the bike to back off a little top end so it's not screeming it's nuts off rather than gear it very tall for top end then in the woods you are on the clutch all the time as it is running away from you!
What end of the country you from? loads of clubs doing H&H racing now
Fast eddy holds events all over midlands-wales-devon
Dirtbike-trax/True grit offroad Hold events mainly around yorkshire
A good site is Enduronews they have most of the events from all the organiser's on there