We take a shovel and dig out a hole for our belly to fit in... LOL..

What I found is that the neck muscles will quickly develop and the sore neck will be a non issue if you shoot regularly from prone position. I also think that the lower you can get your rifle to the ground and still be able to get behind it comfortably the better. On a string with slow slow pit service, I still notice my neck getting a bit sore by the end, but I'm never looking down, I'm either in my spotting scope watching conditions or looking through my scope waiting for the target to come back up.