gpm has the worst info available for our cars , almost as bad as hpi usa.
You have to goto gpmracing.com.hk and then goto news , because they are too lazy to put the r40 into the regular option part dir. Even though Ive seen it in the news section for probably over 6 months.
Part # HR4016 , see if your gpm dealer can snag one for you.
Further part #'s can be referenced from here: http://www.gpmracing.com.hk/car/page/hpi_nitro_r40.html
And photos are here:
K Factory - Cant find jack on it , but saw it in person , jea3 aka JOE of CVEC has it.
Sage Racing - ebay
Hardcore Racing , cant find anything on it but saw suggestion of it. I will try contacting them and k-factory about these invisible parts.
As of all the chassis I cant say which is the best yet as I havent tested them. But my guess is all cars and tracks arent created or modified equally. So my best chassis pick , could be your worse.
I will say this though. I used to believe stiffer was better in the chassis department for R/C's. I think it might have been true for earlier sloppier cars. But for the R40 and PRO4. It seems the thinner and more flexy the chassis the better it handles rougher surfaces....aka asphalt tracks. Where as indoor and whatever smooth tracks you might find can use a stiffer chassis.
What gave me the final clue for the R40 is the new hara chassis says this:
"The R40 Hara Edition has lower centre of gravity due to the new radio equipment layout so that the receiver battery can be mounted "on" the chassis. The chassis is thinner with better roll performance
. Rigidity and roll performance are well balanced at a higher level" - from hpi usa.