My wife can sit easily with the bags installed. She actually prefers it because she can rest her legs against the bags, which makes her feel more stable and secure.
My bags came with the mounting hardware. I got them several years ago on ebay, so I don't know exactly where the hardware came from, but they were originally on a 750K0, so they bolted right up to mine. By the looks of the hardware that came with mine, I'm fairly certain it was mass-produced specifically to fit these bags on a wide range of motorcycles.
Considering how many of the sohc4's had hard bags a few decades ago, if you're patient I bet you can find a decent set for sale that will bolt right on to your bike.