Can I Drill and Screw Here?

I'm replacing the round 4" sewer hose holders with one made from a square 5" PVC fence post. I'd like to mount it up against the front wall of the grey tank. The pan under the tank and the tank are held in place with a galvanized bar running from right to left and galvanized straps running front to rear. The bolts/lag screws holding the straps also go through holes in the bar, using only every other hole. I presume they go into a frame cross member.



Is there any reason why I couldn'tt use two of the unused holes, drilling into the crossmember, to hold my new hose caddy?



I would be using much smaller hardware, probably #12 or 1/4".



Thanks,



Al