I have created a forum specific for discussing SENS:
http://z3.invisionfr...dex.php?act=idx
I hope that I see there a lot of Imminst members.
Aside from reinforcing John's statement, I speak from experience when I say that free message boards are the absolute least reliable thing you could do. Firstly, most people avoid free message boards since they tend to crash when more than a couple of users are on there simultaneously, secondly, there is less control from an administration standpoint, which becomes a real problem if spambots or trolls decide they'd like to turn your board upside down. I commend you for your initiative, but speaking from experience, I would rather see people be drawn to this message board, and the MF message boards, than just splitting up people even more so.
On a positive note, if you do want to start up your own message board, I would look into real web hosting. You can generally find hosting for $2-3 a month, and domain names can be relatively cheap ($10 a year). But as I've said, ImmInst and MF both have exceptional message boards.