That’s a start. Four ounces per square foot is a good target for wing loading for flying indoors (unless you have a REALLY big site).
So - let’s take that Catalina as an example. It’s advertised as 1/28th scale, so it has about 1/784 of the wing area of the full scale airplane, or about 1.8 square feet. That means to get to 4 ounces per square foot, the all-up flying weight would need to be a bit over 7 ounces. In that budget you’d need two motors, two ESCs (if brushless), the drive battery, at least two servos (rudder, elevator), a receiver, as well as the airframe and covering, linkages, and so forth.
Quite a bit of sanding at least.
The Catalina would also be complicated by the nacelle position, which only leaves room for 4.7 inch diameter props at that scale. Finding a motor/prop combination that would work at the right air speeds would be “interesting”.
The numbers are similar for the Guillows B-17.
I’ve seen the Guillows P-38 done as an RC model powered by a pair of G-Mark .03 glow engines. It was a fast handful to fly outdoors. No way it would work indoors in a site smaller than an indoor football or baseball stadium.