I have the same issue and a couple changes really helped me. I switched to Sitka Stratus bibs that have double zippers all the way to the hip, so I can unzip bib front and open the legs all the way up on the walk in. Sounds simple but it has made a huge difference. Also, I switched from a backpack that always made my back sweat to a Badlands Monster Fanny Pack that holds a boatload of stuff and has a shoulder harness, but keeps everything on your hips, thus letting my back get more air. Between these two things I think I just heat up so much less than before that the sweating has become a non issue for me.