Perhaps part of you problem is that a tri-recs block is NOT the same as a flying geese block and cannot be treated the same way. If it is a new technique or block to me, I always practice on scrap fabric first--until I am happy with my result. There is a definite learning curve to using the tri-recs templates and sewing the blocks. I found them much more difficult than regular flying geese.
Try drawing the pattern on graph paper and then use scrap material to see if it would be easier to paper piece. That might help with all the diagonal edges. You can still use the special rulers to cut the needed pieces.