Hi, Margaret -
If I'm understanding right, you can't trim the larger blocks because you will endanger the points. Is it possible that you can trim a side without points? (not sure how your blocks look).
If some of your sides are just slightly short, you can compensate for that by not matching the adjoining block edges exactly when you sew them together (drop the short side lower). You will just have a slightly smaller seam allowance for that piece. I usually put white chalk on the offending side as a reminder during assembly.
I don't know that I've seen a hunter's star with sashing, but now might be a good time to find out if it will work. A narrow border of the required size for each block can solve a lot of problems.
hugs,
Charlotte