MacGregorSailors.com

Just saw this, perhaps of interest, Helper Springs.

https://www.etrailer.com/dept-pg-Traile ... Springs-75

While I don’t have experience with the ones referenced,
There are also other similar products to improve rear axle capacity for tow vehicles that fit in to replace the OEM vehicle snubber pucks.
A good brand that I am familiar with is Timbren SES.

These are designed to fit and transfer load along the design load path between the axle and the frame.

Relatively easy to install and really help.

I added Air Lift bladders to my Toyota Sienna, and they actually did help keep the tail up. The advantage is that you can reduce the pressure on them when not towing and have a basically 'normal' suspension.

Not my photo, but this is what it looked like:

Just remember, however... adding helper springs or Air Lifts to your tow vehicle may help restore the ride level, but it doesn't compensate for the needed braking and sway control - only bigger brakes and mass can do that.