Do the H4 conversion and you should be fine...I have the Raffles 41mm DJ and am doing the same thing. The hour wheel and cannon pinion are really easy to swap. The fourth wheel is easy for a watchmaker...I usually take both the train bridge and winding bridge off, remove the ratchet wheel, balance, pallet fork, and escape wheel, replace 4th wheel....install the escape wheel and train bridge and winding bridge. At this point, turn the barrel to make sure the train rotates...if it does, reassemble all remaining parts.
You can try and just remove the train bridge and ratchet wheel to do just the 4th wheel, but I have found sometimes with the 4th wheel pivots can skew out of the train bridge jewel as you tighten it down...that is why I like to disassemble everything to make sure the train all works before I tighten it all down.