Many of the used guitars and necks I have bought, its not possible to get evry much relief. In my expeience, most truss rods are tweaked, unless of course you have a new or high end guitar probably. For example, I am just getting thre final set up done on my Les Paul Special ( 1999) I got used. It will crank forward no problem, but when you go to crank some relief, it will not get very much till the truss rod gets loose. I'm willing to bet money most used guitars are like this; just check..i bet yours are too.. Truss rods in general are lower end guitars, and used parts guitars are screwed up.
I've had to get rid of some very nice necks..moist form USACG, and a couple form Warmoth cause of this. OTOH I've got several Warmopht necks that work great. Interestingly, my Fender Squire neck truss rod works great. Forget about old Peaveys like the T models..those necks are all twisetd and the truss rod s do not work- terrible guitars.
I actullay like a fair amount of rellief on Fenders and Gibsons, then the frets 100% level and the action cranked low to the max.
On flat radius Jacksons, I like just a tiny bit of relief.