Thread: Using hard items as rests

In general terms how much padding should you put between your rifle forend and the hard item you're using as a rest (tree, fencepost etc)

Specifically, I want to be able to use the top of my Tatonka Stealth 35 pack as a sitting rest (Resting my rifle forend on the top of the pack while holding it steady verticle with my left hand). There is a portion of the frame that runs across the top of the pack under a couple pieces of spongey fabric. Will this be enough isolation or should I look at putting some sort of extra padding or something?

Thanks in advance.