Re: schmidt&bender A8 reticle help
No problem using a plex reticle for rangefinding. In fact if the subtension is smaller than the milliradian, it will probably also be more accurately applied. Just remember to use it just like a 2-unit "mil-dot", i.e. 2 plex post tip to x-hair units. It'll be a bit more accurately applied this way than using it like a 1-unit mil-dot from plex post tip to plex post tip.
Don't expect "stadiametric rangefinding" to be accurately applied on game animals that vary in size a lot though--deer, elk, etc. Just today whilst hunting coyotes i had the opportunity to reticle-range a doe antelope at a guessed 14" back to brisket using the Burris Ballistic Plex reticle. I guessed .8 of the 1st to 2nd lines down (3.0 inch per hundred yds.) from the sitting position--not seaddy enough really for the most accurate "mil-reading". It lasered at 625 yds. Here's the equation--
14 x100 / 3.0 / .8 = 583 yds.--NOT CLOSE ENOUGH!
I have found stadiametric rangefinding accurate on most game spp to ~500 yds. max. Stadiametric Rangefinding is the best application of the SWAG acronym i've ever seen really.