Pick either the cheapest or the weakest.

You want participation, that's how you get it.

And put it on an airplane that is either perfectly suited to it or somewhat larger than that.

Club racing is about the flying. And you'll have some members who look at the plane/engine required and make the purchase decision based on whether or not that investment be pounded down a rathole or usable for other things. Speaking of RATS...........

C/L used to have a racing event call rat racing. It became hugely popular when men were men but then started refining. The refinement went to very expensive and harder to handle engines and the everyday engines and lowbudget racing went right into a rathole. And the event very slowly went in too. And even some of the real men wandered away. And along came slow rat. And Fox rat. All were cheap to get into and promised limited performance. And that event exploded. Cheap engines, low tech airplanes.