The mounts on the stock seats are built in so you would end up raising the seats instead of lowering them by adding another layer of mount unless you modify the stock mounts to fit but then you could do that and not have to buy the added mounts.
I will take another look at the stock setup, there might be a way to notch the stock floor location where the seats bolt onto but most are not willing like I am to take such measures as it is a serious structural part and would need to be compensated for properly.
My last race car was a major issue in this as I moved the seat back to the hump under the rear seat that had the fuel tank under it, notched the tunnel to move the seat more towards the middle of the car and used a very expensive full race adjustable steering column the same as used in NASCAR. The seat mounts were then tied directly into the roll cage and I used a full race pedal setup as well.
Just saying all this so you understand that experience is behind what it would take to lower the seats in this car, I have made hundreds of my own including building full roll cages, etc.
Sadly it is quite apparent no mounts are going to help you out unless going to the right aftermarket seats which will need to be fixed back and locked in place.
If you do a lot of errands, into and out of the car often that route gets old very fast, especially if you use race harnesses, I have done so and my fully streetable race car had 8k miles on it in 5 years as just not that fun after the first few errand runs.