I've seen the US Car Tools subframe connectors that weld to the floor pans and thought they might provide more rigidity than the type that don't. Any opinions?
Slitting the floor and installing through the floor rectangular tube of fairly large cross section (2X4, 3X3, 3x4, etc.) welded to the crossmembers and where it butts the floor panels encroaches on the rear footwell space, but is generally considered the most rigid.
Unless the under the floor full section rectangular tube type is made of considerably thicker material, the contour, welded to the pan style, are considered similar in strength. They just look more like they were always there (almost factory), are much more difficult to install, and some feel the point where they thin down almost to the floorpan is a weak spot and allows some flexing. Extending them down in this area with a tapered box section to regain some cross section height would alleviate that concern and wouldn't impact ground clearance any more than the full box section under the floor type.
