3dmax model to unity scale?

I have a tricky question... My team is making a 2d game and we have a set of complicated shapes that needed precise colliders. To make a long story short the best method we have found for creating the colliders was creating compound colliders using a triangle shape that we created in 3dmax and using this triangle for creating a primitive collider in unity. The problem is that the 2d shapes that we use are created by our artist using a precise grid in his graphic software and the triangle was created using a texture that fits that grid. Now we cant figure out how the scale changes when we import the triangle to 3d and from there into unity. We want the triangle collider to be pixel perfect and when its scaled 1,1,1 to fit exactly into our 2d shapes, but we just cant figure it out. Right now the triangle is very small when we import it. Any advice? p.s: sorry for the long post....