Strange to hear. 17" monitor - is huge. As I undestand huge monitors began from 24"W or 21".
There are some CMS system that already has that functions.
I try to explain: it's a pitty, but some peoples has't good vision! And they try to increase font!

As you can see we have only 6 lines of text with no more than 6 words in each! But together with we have lost space in the right and in the left (smiles already appeared in the toolbar!). And space at the bottom also missing.
There are different purposes of the forum. Some technical forums where - "how many...?" "approximately ****", or "I am do ****" "Yes you may" -- has sufficient space for talking. But if the forum about literature? Or some club for interests? And again - if some people has insuffitient vision?
That picture from the 17" with resolution 1280*1024. Believe me it is not huge!
That'a why I suggest to have two options in editor: if you satisfied with window - no problem, if not - you have the special button to increase it!!! It is time to do that to my mind!!!
Best regards
Sergei