I'm not sure what's the problem at your end.
I had not problems using that font in a text and I could enter a size between 1 - 999.
What happens when you open the form in Acrobat or Reader instead of the preview?
Tx for reply.
Same thing happens in the end result PDF in Reader. The font size is adjusted in the form view, there I can indeed adjust to 999 but when I do that ( or in my case 120 ), the preview and now also the actual PDF show it as smal font.
Can you share your form?