You can't be certain of an exit hole and entry hole is important, I agree. That's why I asked if Spitfires make good entry holes. Based on the responses it seems typical to get about a 1'' entry hole with Spitfires,with a large exit. If I use a fixed head I'll have a 1'' entry and exit.

That being said, I've gotten a pass through on 19/22 deer. Sixteen of the deer were shot with mechanicals, 12 of those with various Rockets. The only 3 times I did not get a pass through was when I used a 2'' mechanical (twice) and when I hit the spine once. Majority of the time I've had about 57-61# of KE (last couple of deer I had about65#).
I now have 75# of KE. If I shoot a broadside (or slightly quartering)deer and only hit ribs I expect an exit, based on my experience.