5.9 Magnum pushrod measuring questions

I am admittedly unfamiliar with Magnum engines and their pushrod/rocker arm setup. I had my original 5.9 roller cam reground, reusing the roller lifters and installed a Fel Pro 9898 head gasket . Only thing changed from stock was the regrind. Installed lifters and torqued the heads down. Using a checking pushrod, I've held the rear of a few rockers up to remove any slop, then adjusted the pushrod until it's tight enough to prevent rotation. Took it out and measured it at 7.075. The other rockers measured within .005 of that too. I read many times on this and other sites that Magnums like a lot of preload, so I figure I'll add .075 for a total length of 7.150. Is this a reliable method for figuring pushrod length? Is there something I have missed to accomodate for the lifters not being "pumped up"? Any answers would be appreciated. If I'm way off please point me in the right direction.
For the record, this isn't the best design I've ever seen for rockers and pushrods. Even Chevy's have SOME adjustment. These? You're good...until one dimension changes in the valve train, then you're SOL and buying parts again.