Charles has a couple great points.
It doesn't matter if the scales are off a bit as long as they are consistent thru the race night.
The other about the tires is on too I believe. A tire will get harder, not softer after going thru heat cycles I do believe. I say I believe because we're poor folk and run tires till they are used up and we use the touchy feely gauge around here. I never had one feel softer, they always seem to harden up. Someone correct me if I'm wrong but they look for too soft a tire not too hard a tire.
I like our racing. Two rules, no nitro and a 500cc limit. That's it. That's when four wheel racing was best also when there were basically no rules.