That's pretty much the best approach. You are trying to turn a sports car into a station wagon and it won't work well.

FBinNY's technique for obtaining more clearance will work with track dropouts since they have a lot of slot length to allow chain chain tension adjustment so giving up a little is no big deal. Most vertical dropouts are just deep enough to enclose the axle and shimming them on top can leave part of it unsupported. Not a good thing to have.