I know we have always been concious of having too many classes but I think Mini's are potentially a good option

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I agree with you Maz, it's not necessary to limit the choice of speed controller as it makes little difference. And agree that the formula/ rules adopted by other local clubs seem to work well and racing is always close regardless if you are running a basic setup with a few modest mods or hopped up with all the bling and blue imaginable. Certain mods make a difference like the alluminium shocks and m-grip tyres but these are not too expensive. Key controls I think are standard tin can motor, pinion size and battery capacity. Suggest getting thoughts from the likes of Ian D and Chris H, they will be able to give some good advice on what has and hasn't worked at MK and LB. Also need to be prepared for interest being bigger than one heat!
With regard to mardave, I have a fondness for them (don't know why) and I am currently on a quest to make my mardave competitive with the mini's at MK (and failing so far

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But if you want some close stock-esq racing, arrangements at other local clubs with the mini's seem to be working well. I also think it is an easier and more consistent entry level for new-comers.
Paul C