Support for flagpole bracket on vinyl siding
I would recommend what you suggest about puling the siding piece, I have done that with great success, filling behind vinyl siding for deck ledger install.
In your case, I would use plywood that is the right thickness, that fill the backside of the siding. Since the dutch lap will require the strips to be narrow, using plywood will keep the backing intact, since it will not split when the screws go through it. Fill it up as much as possible,using pieces that are 8&quot;- 1' long, keeping above the lower piece enough to allow for movement, just a paper thickness will do.. I do not know how the mounting block covers any holes in the siding, but with the siding properly backed up, in my opinion, you will not need the mounting block. Let the screws grab the well attached plywood behind the siding, as well as the wood siding and subsiding. That should give you approx. 1 3/4&quot;+ of wood to mount to.