Without remembering the math, a smaller gauge wire like 21awg would need more windings to be equivalent in magnetic strength, so I would expect the coils to be sorta similar. But there is a lot more to the formulas than that. Best thing is to do is replace with the correct coil. As for the "gives" you mentioned, remember the 2 windings are in series during the hold, so yes the coil could have weaker strength overall in both of its duties. Power stroke = heavy winding only (high current), hold = both windings, (Low current) for max power the eos switch should be gapped maybe 1/32" when flipper is in hold position.