So I hit 999 “perk” points and figured it was still counting but limited to showing 999. Well, turns out that it stops counting at 999 and I should have recognized that the little star wheel wasn’t filling up any more.
Just a heads up for anyone that might think the points are banked.
If you’ve got that many points, does it really matter anymore? 
If you are trying to complete 50 car masteries for the Hub then you will need far more than 999 skill points in total. I think even sticking to common cars with the least skills you need roughly 50 points per car, while the Legendary cars can take 100 each to complete them.
Good to know there is a cap before we reach it, so we can atleast spend the points rather than waste them
Just perk up a few cars and you are good to go again…
Best Advice 
You can find in under u’r Forza Rewards Overview, by tapping on the Burger Menu Icon in the top right corner of the page
The 50 car masteries can be done for 50 points it does not mean you have to fully upgrade 50 cars just spend 50 points unlocked for me before had fully upgraded 2nd car
For the achievement, yes, but not for the Forza Rewards points. That has to be 50 separate cars mastered.
At the very least you need 2,100 perk points in total for 50 completed car masteries.
The cheapest cars to master are the common cars, recognizable by their green frame. Those cars only have 8 perks and take 42 perk points in total. 50*42 = 2,100.
ok missed that were do i find it
Top of this page, under Rewards - Overview - Click on Forza Horizon 4.
thanks 18 to go 8 days driving and last 5 achievements or possibly 2 if skip the drift tied ones but still will be the only game ill be playing for foreseeable future