I have this problem, if i read your problem right. It takes me at least 40 minutes before I start feeling any bigger in a girth routine, however, I find I look fatter once I've gone flaccid and taken the clamp/cock ring off.
However, if you are new to P.E., I wouldn't clamp for 40 minutes. I use a cock ring and my hands too, I've never used a cable clamp so I don't know how different the intensity is. An idea is the [words=https://officialhydromaxpump.com/?uid=6&oid=2&affid=98 ]Bathmate[/words]. It's expensive but it really does the job really, really well and my gains would be much, much less without the [words=https://officialhydromaxpump.com/?uid=6&oid=2&affid=98 ]Bathmate[/words].