Howdy Zach,
I'd like to find a course that is affordable as I can't afford most of the classes that I've seen going for $200-300. How much do the Abate courses go for? I only plan to ride the bike around the country where I live and up to the mountains to do some trail riding and shooting. I've been thinking of making a frame mounted holster to carry my shotgun on.
Keens; I'd highly recommend the MSF course. My girlfriend took it over a weekend and went from never ridden, to a very proficient rider in two days.
Also, regarding the shotgun holster; There are repro M1 Garand Scabbards available (ebay, etc) that work very well for a variety of firearms. The photo below is one mounted on a Ural; Though you could mount one just about anywhere you want on another bike.
Also, the MOLLE shotgun scabbard from Voodoo Tactical should work for just about anything you need:
http://www.voodootactical.net/p-34-molle-shotgun-scabbard-fits-18-inch-remington-870.aspx
Personally I don't ride with a rifle. I figure if my 10mm Glock can't handle whatever comes out of the underbrush, I need to be riding/running away fast. About 4 months ago I had an "Oh ****" moment when rounding the corner of a backcountry byway, I surprised two Grizzly bears. My dog started barking and my hand went to my hip, just as they started scrambling up a hill to get away from me.
If it had gone the other way, I'd probably would have had about 4-5 seconds to draw and shoot. Probably not enough time to draw a shotgun/rifle, chamber a round and shoot.