Actually, there were three different issues of which #1 was fixed by the Hard Start Cap and #2 is masked for now. The third problem was with the Generator.
Problem#1, A/C was starting hard as suspected... ~62A peak @ startup with burdened Humm which took a second or two (no significant voltage drop on wiring) and ~40A after the Booster cap with a very robust and immediate start. The slow start was blowing a GFCI breaker in Tommy's garage only sometimes, but not the regular 15A outlet breaker that is not GFCI.
Problem#2 which still confuses me some. Possibly, the Neutral bonding somewhere needs to be improved as it only take ~5mA (1/5000 of an Amp) to trip a GFCI. I think the 62A at startup is just high enough to get to the trip where 40 amp is not. This can be an issue in campgrounds and etc. depending on how the Neutral and Ground is bonded and where and how long the wire run and etc.. I'd need to dig into this a little more to figure out how to avoid that on GFCI's that are not in the camper. (don't think there should be any bonding in the RV and I didn't see any where Tommy wired up the panel?) It is possible there is a leakage current somewhere... but if it was the insulation breaking down somewhere, I'd think it would do that during normal run also given it is the voltage that breaks down the insulation to where current can start to trickle.. The voltage is the same +/- a few volts regardless of the current. ?? If it is a leak, it will only get worse over time. Any ideas on this one guys? Could be problem with the GFCI and the high current @ startup spike... maybe something inductive into the GFCI sense circuit? This stumps me some, but clearly a lower startup current made a difference to the GFCI circuit.
Problem#3 Affected by #1 and #2 also... but after running a while, I noticed the current going up on the compressor. Voltage was dropping. Then wham, one of the the breakers pops on the Gen... Tommy has it connected via the 30A outlet on the Gen, which some don't realize is a 30A outlet with only 15A capability (shares breaker with one of the 15A outlets) .. I moved to another outlet on the dual 15A outlet, and no problems. I didn't troubleshoot the gen further because I would have had to take things apart... but the breaker or one winding on the Generator may have an issue (most likely the breaker... but couldn't get to the back of it without much disassembly to verify).
Tommy is happy now as he can run the A/C this summer on the Generator and Shore power.. That was the goal. The A/C unit runs about 12A with Compressor working and the Fan on high.. so any 15A circuit should work all day... but the weak ones will warm up and occasionally pop. With the max startup current improvement and decreased duration, then Gen does not choke and stumble... but increased speed as expected.
Note on Generators that advertise 4000W 240VAC or 120VAC. The 240VAC is two 120VAC legs 180 degrees out of phase. The 30A 120VAC outlet is only one leg of the Generator winding and capable of only 1/2 the Generators output power albeit connected to a 30A outlet for convenience to most RVers' with thier 30A plugs . You can use both 15A outlets on different devices to get the full 4000W. So... running a 13,500 BTU AC which is overkill on most small campers will cause issues when using some generators that advertise 4000w or even 5000W. If they could run off the 240VAC... it would be fine.
Bottom line... glad I could help a friend out!

BTW... a comment.. this Supco Booster allowed the AC to be turned on and off rather quickly and it would muscle through the high head pressure without much effort and not tripping a breaker and only a little bit of a stumble on the Generator. Without the Booster, it would choke and stumble as you'd expect..