We used bolts instead of screws to install the e track in our cargo trailer. We were looking for more strength than a self tapping screw could provide. We made a quick video showing how we did it and some easy install tips.
i'd just use a rivnut gun on solid tubing areas for optimal threads, make sure my floor is sheet metal or diamond plate so i can use 1/4" pop rivets to secure the rest where there isn't any and get way more load bearing the rivnut gun also has the perk that if a rivnut ever goes bad you can drill it out and replace it quickly instead of doing structural work for threads if you want the tracks very permanent just weld them down to the sheet metal flooring drilling to the support frame areas to make a weld pool for full securing, add on a roll on oil resistant shop floor coating and you are set for rust and can load even some large tractor parts no issue also don't forget that you can mount these on the wall beams as well so you can use the 2x4 e track clips to separate cargo or keep big bulk stuff from shifting, does double duty for a wall too
No need to go thru your floor with bolts.Get a blind nut kit and just install them in to the wall of your cross members and you will have 1/2" of threads to bolt in to
What you strapping down in there a tank? Absolutely not necessary at all. Good self tapping screw is plenty. If you are that worried bolt through the wood, and use plates or washers on the underside. Some people just install that way and dont even use the frame rails. You are just putting unnecessary wholes through the frame rails.
