Mitch, I did just the opposite and with the opposite results!
I was looking to power a Corgi PCC trolley and the old Bowser power kits are long gone or findabe. So, I bought an IR Birney and after much fiddling and rebuilding, got it to fit into the PCC trolley. Testing the IR mechanism before placing it into the PCC and it ran fine all over my trolley line. I put on the Corgi shell and it would not run at all! Turns our the IR mechanism is so wimpy, it would run the all plastic Birney but did not have nearly enough power to run with the heavy Corgi shell! So, my beautiful Corgi trolley is now a shelf piece and the IR mechanism waits another brain storm!