Thank you for sharing your experience with the Rotec Aerosport external alternator kit. It's great to hear that everything bolted up fine and that you were able to make the necessary modifications without too much difficulty.
It's understandable to debate whether to keep the internal regulator or switch to an external regulator. As you mentioned, you have a backup alternator, so the risk of a regulator failure causing a complete electrical system failure is reduced. However, an external regulator can offer more precise voltage control and protection features such as overvoltage protection, which may be beneficial in certain situations.
Regarding the propeller spacer issue, it's good to hear that you were able to find a solution by taking the spacer to a machine shop. It's important to ensure proper clearance between the cowling and the propeller to prevent any potential damage or interference.
Overall, it sounds like the Rotec Aerosport external alternator kit was a good value for you, even with the minor inconveniences.