Progressive 444 HD's are great shocks, but they're not made to handle 400+ lb or some such two up load, a massive trunk probably also full of stuff plus a trailer in addition to that.
They work beautifully for me, anyway, one of the best upgrades I've done to the bike.
But if you're going to load it way the heck up and add a trailer, calculate the actual load and contact someone like Hagon or someone else who builds shocks to spec and get them sized for that.
As for ABS, yeah there is a fair bit of work to re-fit everything but it's doable. I'd do it if I could find an ABS bike for reasonable money, but no bike over here is reasonable when it comes to cost. Plus, I do like my black/red color scheme, nicest one they ever made on the R3T.