Now, if your problem is not the
height of the head....but the
design of the head, you may want to consider changing them out. I don't know the layout of your system and how much radius each head is designed to cover, but if you can switch over to a gear drive, rather than impact, this is the most popular brand/model in the industry - the Hunter PGP:
https://www.sprinklerwarehouse.com/Hunter-Sprinkler-Irrigation-Lawn-Rotor-p/pgp-adj.htm
When I buy these, I try to get them with the nozzle already installed - usually the #7 nozzle, which is adequate for most applications. You still get all the other size nozzles, but it saves a step for me. Sometimes you can't get them this way (nozzle pre-installed) which is OK too.
There are other rotor gear drive brands out there (Rainbird, K-Rain, Toro, Orbit, etc.) but I prefer the Hunter and so that is what I recommend.
Even going to a different brand/model head, you may still need to raise your heads up per my previous post. You may have some heads that are perfect and some that need raising.