Jimbo,
You hit on my absolute favorite recipe for venison. The only change I make to grill it is to add some olive oil into the marinade to give it a little extra moistness so the grilling doesn't dry it out. I've passed this recipe off as "beef" many times to unsuspecting people. When I make it for myself I let that meat spend very little time on the grill as I like it a little on the medium rare side.... for other folks I tend to have no pinkness in it as I don't want to scare them off. Along with backstraps, I've also taken odds and ends sausage meat and marinated those (need a bit more time than backstraps) in this same method and grilled them. What works best for this is a fish basket or such for the grill to keep them all contained and be able to flip them easy. Dang it... I had some marinated up for last night and the grill wouldn't start... I ended up simmering them for a bit in a pan and they were ok, but now you're reminding me of how good it could have been!