Well, that sets the wheels turning. I guess I'm going to dig in a bit more on flap design and wing "beefing up."
One idea I've seen is to have compression members bracing top and bottom of spars instead of just the middle.
Correct, similar to the N brace at the lift struts but primarily you need to transfer the upper and lower flap attachment loads forward to the front spar. If the flap has a greater cord the mounting loads are actually reduced at the spar since they have a shorter moment arm back from the structure. Higher loads yet less moment arm.
A year ago my project was to use a wood structured wing. I was going to use Vee braces to carry to control loads forward though the structure. I have evolved from there to achieve my design goal but am still not fully locked down on details yet. I do not need to be yet.
You are scratch building so you are open to many options to achieve your desired goals. As with me on my project, you are building the fuselage structure first. This is very good since once the main fuselage is built there is still a massive amount to do to build out the systems prior to covering.
It is during the main structural work on the fuselage that you do your final design and planning for the wings. There is no need to be stuck with what was provided 70+ years ago when you can benefit from the decades of what has been learned since.