Any time you drill a hole in tubing, you make a potential weak spot. Acceptable in none stress areas and 1/8" or smaller holes.
Alternatives are;
- Drill all the way through, welding in a small tubing for 'through' bolting
- Weld on a tab with a hole for using a multitude of available nylon or metal fasteners and clamps
- Purchasing / machining a 'double' clamping device that clamps over the chassis tubing and also captures your smaller diameter fluid tubing