A good lifting belt worn properly under your wader would probably help, as long as you just wear it occasionally it will not weaken the tummy muscles. Of course doing a few crunchs everyday helps along that line also. In addition look at some good insoles in the shoes. My hiker friend recently recommended I go to REI and get insoles for my walking shoes and Wallyworld has the new Dr. Scholl machines to tell you what kind of insoles you need. You will drop a little over $40 either way.

I have a 30 min. routine I do for my back about 5 days per week. It has really helped me keep from having the back pains I used to suffer. Of course, losing 20 ugly pounds would help, but I refuse to cut off my head.