I hadn't noticed it at first, but that picture above captured the historic Wilburton Trestle
in the sideview mirror.
So, first race weekend was a success. The car is a lot faster! Too many variables to know what was most responsible for the improvement.
Porting the intake manifold and shortening/reconfiguring the exhaust to a sidedump megaphone definitely improved power, because I am now able to reach redline in 5th gear by the end of the straight (despite increased rolling and wind resistance from the wider tires).
The car handled beautifully in the turns! Some of that may be improved traction from the wider 3 year old Hoosier Speedsters that I finally put to use on the wider Panasports. But I've had Speedster 205s on my old 6" rims in the past, and never went around turns this well before. It's hard to put into words, I'd say the car feels more stable, balanced, and confident in the hairpins, sweeper, carousel, and transitions through the snake bends. The car has always been very forgiving and neutral with a very slight bias to oversteer, and now feels even more planted in all turns.
No clunking, binding, or noticeable wear of the Nylatron sliding block (thanks again, Dez).
The differential trailing arm didn't punch through or even bend the rear bulkhead sheetmetal (I didn't brace it any further than what I've already shown).
In summary, the changes yielded a consistent ~2.5 second drop in lap times. It's enough to get by most of the Triumph TRs, and to keep the Porsche 356s in sight. The mildly unfortunate tradeoff for the improved performance is that I'm racing alone in a gap between the front runners and the middle pack. But that's okay, it gives me reason to find more improvements to close that gap.
This is a REALLY cheezy pic, but I can't resist. I'll probably pay for this boastful attitude later...
(Man, that cage is tall!)