Insert adapter boot. Can I install it with insert in fireplace?

I have an insert that only has 3 in of clearance between top of insert and fireplace opening. I need to install something like this

http://www.rockfordchimneysupply.co...pg&cap=Rectangle to Round Insert Adapter Boot

Would it be possible to install the boot outside the fireplace, remove the boot then reattach the boot again inside the firplace using a socket wrench? I iwould be using the self tapping screws that seem to be used with this insert (buck stove). Seems like it would work but I have little experience with self tapping screws and plate steel.

Yes that would work. I would definitely pre-drill the holes before the insert is in place in the fireplace. But yes a boot like that will work. Just make sure you buy the right size for your insert.