Not that I've found. In those cases, I create a calculation field in the table the layout is based on, to combine the fields, and use it to replace the merge field.
As long as the first character of the merge field stay on the font size that you want, the rest of it can put made into a smaller font size and it will keep the same font size but shrink the size of the merge field in layout mode.
It is a hack to an annoying issue.
Well, that is certainly an annoying problem. That font size hack was hilarious. Anyhow, I went with etripoli's solution and created a calculation field.
Thanks for all your help.