First of all, the example I gave you was for a RewriteBase of / not /Forums/.
Second, you don't need the RewriteCond for this RewriteRule to work properly.
Third, your RewriteRule that you wrote:
.. does not make any sense to me, sorry (your RewriteBase is /Forums/). Why would you do this? What are the URLs you want to rewrite and what is the desired output.
Honestly, I think you should hire a mod_rewrite person to help you, unless you have a test forum set up and you are OK with learning "on the fly".
I have a lot of experience with this; and it is very difficult to get these vBSEO URLs rewritten in a way that insures you do not suffer a big SEO hit from many 404 errors.
Based on the example you provided and the questions you asked, you have a lot to learn about Apache2 mod_rewrite; so you should not do this "learning and experimenting" on your live forum.