Is your canal a shallow one or one of the deeper ones found in some areas? You tend to need a stronger elastic to set the hook in 8 or 9' than in 3 or 4'. I've used doubled Preston 6 - but certainly not on a canal, as it's pretty powerful and doesn't match lines of 1.5 - 2lbs at all. I used it for tench! Even doubled 4, another I've used a lot, was for a water where carp where regular gatecrashers. For roach in shallowish swims - up to 3' - I use Middy Hi Vis 3/4 through one section, which is forgiving and won't drag fish up to splash on the strike. Slightly deeper water and possible bigger fish, I use the 4/6 through two sections, again very kind on light lines. For things like bream or deep water, I use their 6/8 - surprising thin and stretchy, and still compatible with lightish lines. Sounds like an ad for Middy, I know, but I found them after decades using all kind of elastic and found them ideal. As for Hydro, I use the black one for tench, but I wouldn't really consider that range for light applications like canals and I think you could buy all three elastics I mentioned for less than a pack of Hydro. If you say a bit more about exactly where you're fishing and what you're after, you might get more specific replies.
