Hello David
Testing with a copy of the page would avoid a broken frontend even if the effort doesn't goal.
Yes with typo4.0, but with typo 3.8 if you uploaded some extensions, the site became down 
What did you ask and what do you expect?
Reading the manual I understood that if someone logge himself in TYPO3 with these extension, he will not have possibility to consult or modify his profil except if someone developpe an formular based on the API giving with these extension. So I asked to Herbert Roider if he may be could develop this formular
I still understand even the base featueres of VBulletin because on my own pages I'm using other solutions but I will study VB and your hints will be helpfull.
As forum vBulletin is really great, the best one. There is not only at the level of logging that the interface between TYPO3 and vBulletin is interesting ; for example I used a hack of vBulletin to improve vbulletin's RSS (as RSS OUT). and via an extension I retreat these RSS (as RSS IN) to include them into tt_news. But I have to make this tranfer each time, I think there is easily possibility to integrate both automatically
I understand. We have to think about that too. But as mentioned we also have the chance to change or extend the extension
OK ;-)
à+
Monique