I agree with the timeline theory - a while back it would have been great if the email actually looked like you went to the site and knew a little about it
That said - nowadays, the problem you will run into is that so many tgps are owned by the same group or person, that the overlap of emails would make it look like spam
One suggestion would be to actually hit up the tgp owner on the boards they frequent and ask ahead of time as a friendly gesture - most of them wont bite
(added - I guess that has two meanings - I meant in the physical way LOL - not "accepting" the email way)