Watson--a WonderCut ruler works nicely for HST (I do use starch to avoid that stretch). Also, just read to open HSt, carefully press the corners open and make sure to use the tip of the iron to press the (black) half over staying on the straight of grain. that seems to reduce the amount of stretch.

The best ruler I have found to make HST without needing to trim is this one: https://www.youtube.com/watch?v=NjD3AKiSyPw&t=37s

Thanks for posting. I have nothing to add to the suggestions above, but I'm glad I'm not the only one!

I love my Loc-Bloc ruler for trimming half square triangles.

I always do better when I oversize and trim down.

I love Quilt in a Day rulers (especially the half square triangle ruler) I cut a little bit bigger ... stitch and then trim and they always come out perfect! Good luck

I really don't know too many people that don't have this problem, unless of course as previously stated you oversize it. I decided a long time ago that I would rather trim a bit than give myself more grey hair!

The yellow ruler is horrible to get the cutting lines exactly right. Too much clutter. I got rid of every yellow line ruler I had. I never got a true cut using them.

if you can move your needle I move mine slightly to the side that is going to get cut off. Do this for both lines you drew