What do you use to raise height of your chairs?

We bought a new mh a year ago, and found the same problem, and spent the winter in Florida, sitting on cushions.
This fall before going to Florida I plan on making some brackets to raise the seats. The seats will be raised when we get to FL and be lowered back down before leaving for home. Just used when parked. Don't want to violate any driving laws.
It would be nice to have something that could be permanently installed to change the hight up and down.