John...a certain Frenchman called Jacques Anquetil did not do too badly on his Simplex 543 gears in the 1950s. With Simplex gears back in the day...it was a case of ensuring that you put the chain through the rollers and the tension cage, with the cage the right way up !
Look on any internet- site with a fair sprinkling of Simplex T-d-F gears and the like and, inevitably, you will find quite a high percentage of the bikes will have the derailleur cage the wrong way round.
Norris Lockley
Settle UK