P400- did you have a lot of seat time on your P11 before you converted to JS internals? if so, can you quantify the relative change in engine characteristics- vibration level, power output, etc? Did you rebalance the crank and if so to what balance factor?
I have a low compression P11 and while great on windy country roads, I try to keep the speeds below 50-60. Gets a bit vibey above that. Hard to believe a P11 -even with JS long rods, lightweight pistons - would be anywhere close to a well-adjusted Commando for smoothness at speed.
When I first moved to PA from upstate NY I found out that the state of PA DMV required rubbers on the footpegs. My '66 G80CS just had metal pegs with weld built up on the outer edge to keep your foot from slipping off. I had to buy a pair of Honda rubbers and cut the ends off to fit. Mine had all the street gear still intact although one of the previous owners had used it for hillclimbing in the San Francisco area at one time. "Climbs hills like a Matchless"
In my experience a balanced motor does make a difference. I had my P11 10 years and put at least 8000 miles on it before I got it balanced using Norton parts. I could tell the difference immediately underway. I dug up my receipts to see if the balance factor was listed, but all the receipt says is balanced engine. It was done in 1988. I also owned a 72 750 Commando, but did not hold onto it. I still have the P11.
I can't really compare power level and engine characteristics, because I basically turned the motor into a breathed on Combat engine with more carburetion when I put it back together after I had the crank balanced. It makes more power, and has more grunt everywhere in the powerband.