is there a way to get them to sit lower on the belt or is that generally not advisable.
IMO, unless you're wearing body armor such as an interceptor where a thigh rig is necessary, you should keep the weapon at belt level; i.e., the top of the weapon clears your belt allowing you to fully access the grip to get correct placement of your hand on the weapon.
Besides trigger control, which is the number one priority in shooting a handgun well, how your grip is executed from the draw is the second key to good shooting. Having a poor or sloppy grip during presentation will affect both trigger control, sighting, and control during recoil for followup shots.
Having to reach for the weapon because of unusually low placement isn't conducive to a good grip, and it is no help in gaining muscle memory for concealed carry (CC) either. Most CC rigs are on the belt, either Inside the Waist Band (IWB) or Outside the Waist Band (OWB).
I don't know if you're a CCW permit holder, but if you plan to shoot IDPA, this is the type of rig that you'll have to use. IPSC is another game entirely, where you can use any type of skeletonized Han Solo drop leg that you want in Unlimited, but it isn't reality. It's one of the reasons that I stopped shooting IPSC, and switched to IDPA, too much gamesmanship and equipment races.
The bottom line to me is that you can shoot IPSC with the low mount holster, or use one if you wear full armor, but for anything else where normal everyday carry, either concealed or open, or
reality based competition are players, a standard belt rig is the one to use and learn.