Hey Xey, Welcome to [words=http://www.mattersofsize.com/join-now.html]MoS[/words] ..
Clamping at only a semi is missing the point of clamping ... it's to occlude and expand the tissues with its higher than normal forces.
You only respond and grow to a stressor. That stressor can be pulling on the ligs, or persistent [words=https://shop.mattersofsize.com/products/sizegenetics-penis-extender]traction[/words], or jelquing, or SSJs, or infinite etc, ... but clamping to only a semi (and doing nothing else) is not really a stressor. Nothing is being pushed to that next level and there'd be no reason to expect desirable growth from it.
You can jelq with a semi (indeed that's the normal style) and see gains from it because there are additional manual forces being applied .. but clamping should push the boundaries of turgidity and impose a forceful expansion to the tissues, that's what it's good at, and that won't happen with a semi.