Welding the chassis

[voucht]

Oscar,
I never dared fully welding the chassis stage by stage, but I think it is not a bad idea, if you are sure everything is OK before. For example, the front frame and U1-U2 have to be in the perfect position before you fully weld them, and it is hard to know if everything is fine before placing the suspension brackets (which comes at the end), even if you respect the book's instruction. For example, some people place these tubes using the suspension brackets jig, you will find threads about that on this forum.
Personally, I had to remove them and make them a second time at an advanced stage of the building. so I would have been in the sh... if I had fully welded them in the first place. So I think it is just a question of confidence in your skills, measuring, welding and double checking as shh120m says.
Concerning making a smaller chassis, I did the same, and I'm glad I did it. I built the fist stages of smaller chassis (scale 1/2, see the picture), to practice and try different things. As I couldn't hold the tubes vertically with the bolts-brackets assemblies, as I did for the big chassis, I got distortion. (I used 20x20 tubes for the small chassis, and the holes in the brackets didn't match this dimension, so I couldn't hold the tubes with bolts, as I did with the 25x25 tubes of the big chassis - see pictures).
I haven't fully welded the big chassis yet (but soon !), but I expect the bolts-brackets assemblies to help avoiding distortion (I haven't invented this, I found it on a blog of a Locost builder). So this could be an idea.
Hope this could help.
Good luck.
Cheers.

Small chassis :
Equerres01.jpg
Big chassis :
1erTubes02.jpg
Small chassis finnished
VouchtChassis02.jpg