Whats the best way to install an older version of vtiger on the hub? I need 5.1 .
and went from there. so far so good.
That's definately one way to go (and quite possibly the best IMO). One of the advantages of going the LAMP route is that you can specifically choose which version of vTiger to install (and could theoretically have multiple versions if you wanted to test different features/plugins/etc).
The other option would be to install a legacy version of TKL (if you click on the legacy link in the top right of the screen when you launch a server from the Hub). The downside of going that way is that the underlaying OS is older. The previous version of TKL were also based on Ubuntu (as oposed to Debian) and while Ubuntu is a nice OS, it is more buggy and not as stable as Debian IMO.
More information about formatting options