As cheeky as you are for just posting on the forum and not being ar5ed to post in the newbie section first, I think you have a few fundamental problems with your slider - It isn't really a slider!
Most crash bungs are to stop damage at little or nil speed. If you have any forward momentum then they do tend to tear off, which I am sure yours will do as well as, by that time, the spring will be fully compressed. A slider, I don't think so.
You are correct that a crash bung can cause damage as it may be the first point of impact and therefore focuses the force of impact in one area, normally the frame. Dependant on the bike, and bung manufacturer, some bungs use an engine mounting bolt so that one side of the frame is not taking all of the force.
Maybe I misunderstand but I am assuming that you are saying that the spring will significantly minimise the force of a 400 pound bike falling?