Hmmm ... It must be able to take advantage of mod_ssl.
vBulletin is a very successful community ... It would have had to have been at least modded now.
Why don't you check their forums for hints?

When used properly, Flash definitely has a lot more pros than cons.
The main problem you'd probably face is load time, but with Studio 8, streamlining Flash has been easier than before!
Not to mention you can have your own custom preload sequences .....

Bottom line is, you just have to know what ...