I use the GS2572 with my L2501 HST and R4 loaded rear tires. I've do a section of our unmaintained community road and my driveway with loader and bucket, without the bucket, and without the loader and bucket. I also have the QH15, so quite a bit of weight. The elevation is around 4000-4500 ft.
It works great no matter if I have the loader and bucket, without loader, or without bucket. I don't have traction issues, but I run 4WD. I also use it on the back for ballast. It works great for that as well. The roads are hilly. I use M both uphill and downhill although I have to back off the treadle pedal to go up hill with a full GS.
Weight is helpful to keep it cutting the washboards or to use the scarifiers to fix potholes etc. Btw, I've had it about 15 months, and it's used regularly.
On word of advice, do locktite the bolts that hold the scraping blade onto the frame. Mine came loose all of the time (almost every use) before using locktite.