By definition a tensile structure should have double curvature in order to be able to carry external loads. For this you need a minimum of 4 corner points. Add to this that once deformed under external load, the membrane can accumulate water due to rain or snow melt and the water has no way of exiting the surface. Triangular membranes are not a good idea at all.
The first example file here is very close to what you are trying to do:
If you’re watching tutorials, make sure they’re for Kangaroo 2, as many major things changed between 1 and 2. For instance, with 2 there is no longer any need to use the timer.
If the first input on the main Kangaroo solver component is called ‘Force objects’ instead of ‘GoalObjects’, it is the old one, and you should ignore those tutorials.
(also agree with @davidsmavrov - only 3 corners isn’t so good for tensile structures)