I use aquarium running on my take base, both the 27 and the 306w share the base. I find that the soft tubing is actually kind of "sticky"and does not really need to be stretched very much...as a matter of fact I just finished serving all of the final leather edging on my"haver sack" and looking at my machine I would say that my belt is "slack" it gave me no trouble
(I was having plenty on my own...folded edging is a bugger"