I ended up using a stiff canvas bag made by Maddog. Just held in place right now by tie straps, will replace with cable or chain.Has an overhead rack in it, but not too sure if I like that setup. The behind the cab setup allows me to step out and pull my rifle straight out the end in a hurry, if the need arises.No zipper, just an end flab with a buckle. This case happens to be their floating model, might try and find another.
[Linked Image from i.imgur.com]
[Linked Image from i.imgur.com]