Your accident story and mine is similar. I'm on 2nd trike after accident. Bought a 2016 just before the Milwaukee 8's arrived. I've been waiting for quad valve since leaving Royal Star Venture in 2006 when I got my 1st ultra Classic. In went the 2016 and out with a 2017 and finally Harley has some adequate power for trikes.
With 3 back surgeries, numerous steroid injections, physical therapy on neck for 3 months I still could cannot get my Triglide to ride smooth enough. I used Lehman's suggestion to drop air pressure to 20#, bought Goodyear comfort tread tires, bought Harley's Hammock seat, bought Legends air shock system with air pressure gauge on dash and all did not help at all on the bigger bumps with only a little improvement on the little bumps.
We just cancelled a cycle run to Flagstaff from Wisconsin because my back just went out on a 2 day trip to Dubuque (I plotted a course using all county roads and I think the excessive amount of bumpy Wisconsin back roads did me in. Last week I started pursuing selling our trike until I came across 14" pro action shocks by DK.
I will buy a set when our car ride to Flagstaff ends and report back to you and all in Trike Talk. My background is R&D product development and can appreciate you wanting to find a smoother ride on a trike MORE TO FOLLOW::