I did say that to a single attachment point gives 100% as it is impossible to have straight pull from 2 points (unl;ess using a spreader bar)
Another way of of looking at IYT is I is the straight line pull y is the less than 90deg angle and T look like a T and therefore not suitable.
A good way of demonstrating this is to get 3 people and a sling.
Get 2 people to hold the sling standing together and then the third try to pull the others over.
This is the I
Then get the 2 people to separate and make a 90deg angle at the 3rd person. The third person is more able to move the others. Then if the sling is straightened and the 3rd person pulls the middle of the sling they will move the others easily.
Try it and see.
Hope that makes sense
Regards
Crisp Iamge
My humblist apologies Crisp Image, my intention was to try and state what you said in a slightly different format. Re-reading my own post I can see how it came across.
I use that wonderful trick with people pulling in the different directions with regularity myself
Cheers
Daawl