Sakoluvr,
Would probably try Varget first, of the powders you have. With high-BC bullets like the Scenar, muzzle velocity doesn't matter nearly as much as it does with more typical "hunting" bullets. A "loss" of 100 fps at the muzzle ain't gonna matter much at 550---or even, in my experience, at 100 yards.
How old is your IMR4350? Not asking to make sure it's still good, but I bought a couple pounds of IMR4350 a couple years ago, the stuff made in Canada, and it turned out to be "short-cut"! So far it has produced just about exactly the same velocities as the standard. long-granule IMR4350 that most veteran handloaders know so well. It would probably work very well with 150s in the 7mm-08--if you can find any.
