I hate to jump on the bandwagon here as a fellow builder but I would second/third what has been said before. Your single backbone frame has been cut in half and replaced with butt welds that look suspect to begin with. I'm not being a critic to pile on, I'm simply speaking as someone who has done quite a few frame modifications.
I have made mistakes, we all do. I grimace every time I have to pull out the grinder and sawzall and cut off tubing work I spent hours patiently fabricating. But my rationale is my two beautiful children. And wife I guess
Your lower frame work really needs attention. Not when it breaks, but right now. Find someone with a tubing bender and some 1.25" DOM tubing and make some really beautiful bent down tubes. Best part is no welds other than the top and bottom joints.
I know you are rightly proud of what you have accomplished, it's not many that come through the other side of a project like yours. And everything else looks great. Just, PLEASE, take care of those tubes before you forget about things and six months later your posting up in face plant.
If you can't find anyone else local, send me a PM and I'll bend them for you for shipping. But it's much better to have the bike on site to get quality bends.