Hiawatha made a good point - and I do that a lot too - if the tree is too fat at the bottom, just fasten it on about head-high, and you can sometimes make up enough of the difference in diameterto get a good bite into the bark and not be on too much of a slant.

Of course, then there's that bothersome task of trying to monkey yourself uponto the platform fromthe ground.

Other than that, there is no other way. If you want to use a portable, you're always going to be limited in your tree selection.