Nice job. I love the part about "then I knocked out the stringers and junk" like that's no big deal. lol
I'm with you on the prop guard... smart upgrade for sure! Definitely would feel more comfortable.
Your welds are more than adequate... I did want to point out my buddies in custom fabrication always tell me it's better to weld at an angle on channel, so your cuts could have been done at a 45 and then your outside plate would be a diamond shape... so it never has direct vertical welds. Just throwing that down if anyone else wants to look into it. But your solution should not crack, is bullet proof, and looks good. And like you said, the weight distribution didn't even change.
Looks good dude!