Can I screw directly into the frame under the window on passenger van

I would like to mount my bed higher to fit bikes underneath. It rests on 2 frames screwed into the wall about 12" from the floor in our 2008 passenger van. The current screw locations are into the framing underneath the wall panels, but do not appear to be the main structural frame. The write-ups I find here all are in vans without windows in the back, and many frames whether for beds or otherwise are mounted into plywood or cargo tracks installed to the plywood it appears. My max height of the bed would be about 33" from the floor, but the frame under the window appears structural. Can i screw the bedframe directly in? Should I tap it first or just use sheet metal screws?

All advice appreciated.

My method was to put the bed on legs that are secured to the cargo rings in the floor. It required welding steel frames, but is fairly light and easy to handle.
I didn't consider putting attachments to the sides for supporting beds and such simply because of the shear stress on the fasteners and pieces. There could be connections to the sides that stabilize the framing, but not any that would carry any weight.
There really is no 'main' frame in a Sprinter. All the steel you see is welded and glued together in layers to form one big structure. The downside is that to save weight, those pieces are pretty thin and light weight at any given point so making solid connections that would hold weight would require a lot of fasteners drilled into the steel.
That's my theory, and worth just what you payed for it.
Jef

I try to consider materials and strength, but I also try to be practical. I remember reading where a 10d common nail has 500# shear strength. If properly designed most all the force on your side bed supports is shear stresses, not pullout. Friction will also be your friend in most cases.

In my Cheap Tricks you can see how I mounted my bed frame just under the windows using a notched 2 x 4. I used some 1/4" diameter sheet metal screws to hold the 2 x 4's in. I don't allow people to sleep in it while moving, but that isn't because I'm worried about it falling apart, it is because I worry about someone crashing against the side or back windows and falling through. We have been using our bed for over 2 years now. There is absolutely no sign of shifting or impending doom.

Not to be snotty about these things, but if anyone tries to take you down the "If it ever goes to court" primrose path, don't fall for it. If you're unfortunate enough that something you do gets into a court situation you are kidding yourself to think you will out fox lawyers with your design documentation. The lawyers do in large corporate engineered products, how far does anyone really think their DIY engineering will take them?

That said, build things strong enough that you feel comfortable with it and then just enjoy what you have. As Cedarsanctum indicated earlier, this is also my opinion and worth everything you'll pay for it. Have fun. vic