Don't decide you need to scrape the back, finish the tip and then clip it. Results are sometimes unpredictable. Do one thing at a time, and always try the reed. Learn to clip the tiniest amounts from the tip possible. If you can hardly see the remains on the block, it's about right.
Consistency is more valuable than frequent experimentation.
Try to find something that works and stick to it. The more consistent the process, the more consistent the result. Don't keep changing shaper tips, cane suppliers, staples, gouge dimensions, etc. While it's best to keep the length fairly consistent, this presumes that you're using the same cane, shape, and type of tube for each reed. Tying the reed on longer has the opposite effect.