The Friendship star kits we make on the triangulations papers has this formula:
The half square triangle has a finished size of: x" (three inches in my case)
which allows you to know that the cut size of your plain squares has to be half an inch bigger.
I was doing the math again on your stated size: 4 1/2" minus the 7/8" that is what happens when you do your sewing on both sides of the corner to corner line is: 3 and 5/8" ... which is 1/8 of an inch smaller than 3 and 3/4" ... so, you shouldn't have to re-sew your half square triangles, and I would just sew my solid squares where I want them, then trim to the same size as my 1/2 square triangle squares.
Hope this helps.