In a nut shell has any one tried it?

A little background into why I am asking...In September we are off to Scotland for a week, canoeing on a sea loch and camping in the wild for nigh on a week.
To supplement our rations we are hoping for some fish, problem is I'm not a fisherman and when I have tried the results are meagre.
To help me along I was hoping to troll a line behind my canoe, however I have tried this in the past but the line including bait and weight simply skims across the surface.

In my quest to find out how to catch tea I have come across a post regarding a home made paravane...

"Simple tow behind (trolling) paravane method from a kayak, rowing boat dinghy or yacht - works up to about 5 knots speed.
This is the simple method of using a hand line to catch mackerel or other predatory fish – I have had Garfish and Bass to this method.
Cut a rectangle of 15mm thick or so plywood approx 15 -20cm long and 5-8 cm wide. On the centre l,ine drill a 4mm hole at each end about 1cm back from the edge then on one end cut to a 45 degree chamfer - Sizes are approximate and do not seem to affect the function you can change the depth by changing the size and angle of the chamfer but it does not seem to make any difference to the mackerel

Tie the pointy end to a 15 – 30m handline i use a swivel but you can just thread through the line and tie a stop knot - i prefer to use thick paracord or nylon cord as the hand line rather than the thin orange crab lines you buy at the seaside as it does not cut into your cold hands.

Off the back tie a swivel and then attach a 1 ½ m nylon mono filament fishing line with a reasonable breaking strain – 5+ kg is fine and attach a simple spinner on the end. You can use feathers but any simple silver spinner does fine and if towing from a kayak or sailing boat using many hooks on the feathers can be painful. I sometimes use a rubber sand eel which also works well.

A coat of varnish will prolong the life and also make it dry out quickly after use but you can just use

To use drop the paravans in the water so the chamfer angles down, as you let out the line the paravane will take the line down to 5m plus deep. When you get a fish on the fish will swim off to the side which flips the paravane over and then the chamfer works to bring the line to the surface and keep it there.

This works really well as you can then see you’ve got one on and also makes it really easy to haul in as there is no weight and its all at the surface already. If you are sailing or paddling then you don’t have to keep feeling the line to see if you have one.

I used this method as a kid off a 35ft yacht, a 16ft wayfarer sailing dinghy, i now use it off a sit-on-top kayak which you can do off the beach , from sea rowing boats (seine boats) in Teignmouth Devon. It works best at dawn and dusk close to shore int he summer when the fish are feeding, but has been successful out of sight if land in the English Channel , as long as the speed is not too fast.

A small length of cord with a clip on the end makes it easy to attach to the boat to stop you loosing it all.

When you get one, hold out over the side of the boat when you unhook as they will tend to empty their guts, I prefer to quickly break the neck by sticking a thumb in the mouth and sharply lifting up to 90 degrees which breaks the backbone and stops them flapping about making a mess and bruising the flesh. This also bleeds them out as the gills rip."

I would appreciate your thoughts.

Cheers
Tim