Final update:

I went back to the local bike shop and bought the Revere Journey 2-Up seat that I tested last week. I did that instead of ordering a Saddlemen for a couple reasons.

First: I knew it helped already since I test rode it.
Second: I didn't have to wait for shipping
Third: support my local shop
Last: it was like new but used so I got it for a great price.

First longer than a test ride impression: it's got me fixed. Massive reduction in perceived vibration above 2000 rpm, and basically glass above 2500. (as smooth as a 103 ever is anyway).

Comfort seems fine, I felt like I could have gone several hours no sweat. I'll know more about that as I put the miles on.

So total effort to now:
Front engine mount
Rear swingarm isolators
New seat (probably the key item)