2' x 3' hatch? Most people put them under the patio :-)

Considering the price of the circular saw blade you cited, have you
consider a Bosch PMF180?

They will do a thin cut (might be 1.5mm rather than 1.3mm) and can do
a lot more re true "plunge-cutting". Basically a cheaper version of a
Fein Multimaster (some tools interchange).