Too much weight?
I built two cars for a circuit race a few years ago with HWDR. 60 gram and 120 gram weight limits. Charger was 60g and Cadillac was 112g. The charger was faster than the caddy and those two builds won me the overall circuit championship over 8 tracks. I build two heavy weights for D64 that were 150ish grams. F-150 and a zoom in platform. F-150 was faster but it bent an axle on the last test run before shipping. I believe the zoom in was the first mod at D64 to break 420 scale mph and the f-150 was still running 416 scale mph ( sorry can't remember the times) I think it's a balance of wheel and axle prep and centre of gravity to achieve the most speed. I believe there's a fine line where more weight is detrimental to speed and performance. I ran that same zoom in at home and recorded the times. Adding and moving weight around and found that the best performance came at 110-120 grams with weight balanced between the two axles. Additionally weight had no affect on lowering times. If anything it slowed down. Just my 2cents. But everyone has their own preferences and what works for one person doesn't necessarily work for someone else. Testing testing and even more testing is your friend. Ask Blueline who's been at the top for years. It's not by accident he found his way there.
Actually I did put weight under hood.
Hopefully 905 will allow a double patcher