Could swear there are adjustments you can make to change the pressure. But that could be more on your pressure plate design and how many clutch disks you have.
There are several things that affect leg effort.
1) is pressure plate as you mentioned. But I have an RXT twin disc which are known to be very easy to push.
2) Master cylinder bore size. I went with the slightly larger 13/16 to reduce pedal throw for quicker shifts. Based on the math, this should have about 16% heavier leg effort than the traditional 3/4 bore MC. Depending on other variables, that should be about 6-9 lbs of leg effort increase, which isn't that bad.
3) clutch pedal ratio. It's interesting that all the companies I'm dealing with will now say they want a 6:1 pedal ratio, which they should all know isn't the case in a factory 68-72 Chevelle. I think our cars deal with closer to 4:1
4) Rod alignment. Ideally you want a perfectly straight rod engagement into the master cylinder with no flex. I know mine isn't perfect, but I felt like i got it pretty close. Can be seen in previous posts in this thread. I will work on trying to improve.