Fuel/gas/propane lines hanging/drooping on my rv?

I have a few of the rubber gas/fuel lines hanging down on the underbelly of the rv. None of which are for an outdoor BBQ.

Everyone that I encounter says to zip-tie or pin them back up but what do I screw into?

I don't have an issue with zip-tying, banding and tacking back up...my concerns are:
- where do I screw into? I know I need to avoid using a longer screw that is needed.
- avoid the path of the slide outs
- and the cursed....too long of a screw going through to the floor :eek

Where is the best place to screw into the underbelly? into wood? metal frame with sheetmetal screw?

Also, there appears to be many spots under the RV on the underbelly where there are pre-drilled holes in the underbelly where it looks like they should have put in a screw to fasten the underbelly but didn't....did they just get lazy? Are there just more holes then there are actually needed? Do they simply pre-drill holes throughout the entire underbelly now knowing which TT model it will be attached to and have more holes then needed?

thanks guys and gals :)