https://www.youtube.com/watch?v=MV4qVbNPX_w
A Quazar 'replica', but it doesn't say anything about the driveline.
The challenge to covering a motorcycle, is that the seating position is naturally high.
But just for a fun morning engineering brain exercise... The Quazar concept puts the rider lower, but the GL flat-four/six doesn't lend well to such, because your feet would be right where the cylinders were...
Unless you were to move the engine back, and straddle the air intake a bit.... or go separate carbs and keep the airbox low.... move the battery, fuel tank, radiator, etc., all forward... and lower the handlebars... dunno about leading link... but this'd get it down lower. It would (*like the Quazar) make for a longer wheelbase, which doesn't help handling at low speed.
The biggest disadvantages to recumbent position (and this comes to me from bicycling experience) is that you cannot transition weight from hiney to feet to relieve road shock, and the inability to substantially turn head AND upper body for a check of the sides...
But weather protection is really, really important... particularly in California's bitter cold winters, frosty pumpkin falls, and misty spring mornings... :headscratch:
Meanwhile, I'm getting ready to fit up the tire chains on my 1200... :smilie_happy:
So for curves, take several sheets of 2" extruded polystyrene (Formular 250 is my favorite), and glue them together with cove base adhesive. To do this, lay a piece of 3/4" plywood on the garage floor, lay one sheet, glue, lay another, glue, lay the third, then set another sheet of 3/4 plywood on it, then a half-dozen concrete blocks.
Use a cordless sawzall with a coarse metal-cutting blade to slice it down into pieces thatl'll make your straight-and-square setup. Prop it in place over a frame rigid enough to hold it in-situ, then take the sawzall, and your wife's electric meatcarving knife, and whittle it into a semi-curved shape. Then use an orbital sander with 80-grit disk to smooth it out.
For gaps, get a can of hardening spray foam (not the stuff for around windows and doors, it stays flexible), shoot that into the gaps and let it set up, then smooth it.
Once youv'e got it smooth, roll a thin coat of fiberglass epoxy on it, let it set up, then stretch a sheet of fiberglass cloth, and dab more epoxy on it, let that set up, sand the rough edges out, give it another layer or two of epoxy. Once it's set, you can cut the foam out from under it.
FWIW... this was a technique that was substantially employed by custom carbuilders right in your neighborhood... it shouldn't be tough to find some grey-haired guys that'll help guide you through it...