Hi Quirine,
If you already have a quick release belt, there is no need to buy a new one. I have the North system which has a loop on both sides of the belt. At the end of the long line I have a carabiner (Large for ease of use, and unable to come off the line) This end will always be attached to the towed boat. About 15′ up (just long enough to comfortably clear your boat) I have a trucker’s hitch with another carabiner through the loop and attached to my belt on the other side. If I want a long tow it is a simple matter to release the carabiner, pull out the hitch and extend my rope to the full length. Belts sold in Canada have an extra long rope to meet with coast guard requirements and it is a bit longer than is comfortable. If you carry a throw rope as well, you can shorten your tow rope, but experiment before you cut! I don’t remember specs off hand I could can go and measure, or better still let’s get out and have a practice.
Maureen