Pretty Noob Heating Question for MSV

Have a 4x2x2 PVC enclosure that I am going to be adding heat tape to on Monday. Question is this, and I would love to hear others' methods or experience. With a basking temp goal of around 92-95ish for a Darwin, should the body of the snake register that temp as well with a heat gun when in that area, or will it be a few degrees cooler? Heating this enclosure has turned out to be quite a challenge and I am not turned off to the idea of a RHP. Saw a YouTube video with a guy with the same enclosure size who had an 80W RHP from RB and it would not get hot enough. My thought is that I would need the 120W RHP to properly get a basking temp higher than 90* - any experience with this? Thanks all.