Maybe you should look at some of the modern F3A designs as they have much better wing loading than the early pattern models. How do you want it to fly? do you want something precise that just goes slow? or do you just want slow? Thickening the wing and lightening the plane may make a lot of lift but can kill how it flys if you like precision. The UCD flys like a crap compared to any decent extra, edge, or yak with a decent wing loading.. I dusted off my favorite old profile hots with its thick wing and flew it a couple years back and was like omg I cant believe how poorly this flys compared to more modern designs that are lighter with a thinner wing section. Your best bet would be to find an old pattern kit, or plans, and build it with 1/2 the wood IE KEEP IT LIGHT... then it would fly slow and wouldn't screw up the flight characteristics..