Tank on CG is not a major rebuild at all. There are lots of postings in this thread. Yes, it needs either a pump or a YS, but that and a little ply and you're on your way. I played around with both of those options, but I was new and impatient and didn't get very far. Once I started flying pattern I quickly came to dislike the change in balance. Lots of guys have no problem with it, and probably get into a rhythm of when to compensate with a click of elevator here and there.
I have to go back and see what 'issues' you're talking about though
I remember adding positive wing incidence to my plane, and I believe a little change in engine thrust as well. I don't remember all the details other than knowing there was a washer under the engine mount, and a Popsicle stick under the wing saddle.
I have another Venus I will be converting to electric. Should be my next airplane project over the winter. I am going to research a little - want to make the canopy hatch very nice and clean, and am considering at least a little recovering, if not major. It will be fun putting this plane together knowing what I know now