Looks nice- clean. Just how I like mine.
Plenty of room for that 4-banger in there, what you need is a bigger hammer!
I actually look forward to fitting these 4-strokes in a frame, it's forced some pretty interesting solutions.
You might consider removing a link from your pedal chain, and get that axle up into the drop-outs as far as possible... Also, what's called a bicycle chain tensioner, if you're not familiar, will slip over your rear axle, and hook over the frame, and have been recommended for that style drop-out.
Stay with it!