For what its worth,
I think that a limit should be in place regarding the depth of any hamster and knee rest.
Anything beyond a certain depth shouldn't be allowed.
Personally I don't think using rests like the ones in the pics are fair, its too much of an aid, you may as well bring along a table and rest the gun on that.
Plus...if you have all that bolted to you're gun and miss......red face time for sure