You could create a custom version of the report and move fields around as needed (trial and error).
I haven’t done this with the W2 form, but I had to do it to get the alignments correct on our check runs to line up with our check stock; it should be a very similar process.
Found the solution right after sending my previous reply.
Since the report is 5.5" and prints 2 per page it was more difficult than a normal form. The problem was the space between the 2 forms. Originally the bottom printed fine for me but the top printed about 1/4" low.
I moved everything up 1/4" so the top printed correctly. I then extended the page size to 11.5" and the tablix to 5.75". This causes the print routine to look for 8.5x13 paper so we needed to override the page size and set it to letter.