I doubt there are significant numbers to make any difference, these are not ALL boat dwellers only ones who choose not to stay put.
The Sofa surfers will not want to found, that's why the majority are surfing, neither will some of the boaters.
Firstly they have to be persuade to apply for registration.
Then they have to be sucessfull, having met the (loose) criterior, see below, (note under address1)
Then they have to vote, there being no guarantee they will all vote against Conservatives.
Some of those people will be minded to vote so will already be reg