Mike, you have a coach that takes the largest SAFE T PLUS cylinder and within it is a 200 lb plus spring. The TRIM kit was developed by Roy Mueller whom is a BAC member and Roy sold to Hendersons.
We had installed the trim kit as we had a SAFE T PLUS on our 1991 Contessa and then our 2004 Marquis. The installation manual for the SAFE T PLUS notes that you get in a level smooth parking lot, drive straight, then let coach come to a stop without using the brakes. Then you install the mounting kit and the SAFE T PLUS cylinder.
Sounds simple enough and it basically is if you are any type mechanic. Problem comes when road is not smooth, is cupped, is unlevel, etc and then you also have the wind. Holding back on the 200lb + spring when driving a long distance gets very tiring as you work to keep the coach tracking straight down the lane. Basically you are constantly adjusting the wheel.
This is where the TRIM kit comes into play as it is an air operated device that when you correct it to align the SAFE T PLUS with the road surface/wind push you are getting allows the coach to track straight without you doing it with your arms. Very simple to operate once you get familiar with it.
As suggested, install the SAFE T PLUS then you can determine if the TRIM kit is worthy of installing.
We blew a right front steer at approx 64 mph on a beautiful July Sunday morning in Nebraska, with my wife driving. Coach stayed perfectly straight, she slowed with no braking until around 10 mph and pulled off to the shoulder side of the highway. The SAFE T PLUS is worth any amount you pay to have it on your coach. The coach's you see in the ditch or rolled over, or in a scrap yard, that blew tires will not have a SAFE T PLUS on them if you look.