Custom is a crap shoot. Who says you and the builder are speaking the same (cycling) language. There is clearly some fuzziness around OP's description of what he is looking for. I wouldn't bet that can be converted into the "exact characteristics" he wants. Much better for him to try out readily available frames and pick the one that feels best. At least if he can't find any of a brand to try out, it is likely an online retailer would accept a return of a stock bike within a defined period for reason of incompatibility.