Easiest route would be to drill larger holes as mentioned, or just use a jigsaw to cut both holes out to make it an elongated opening (which is my preference anyways)
I was going to suggest the same thing. I have Eheim 12/16 hose which is typically interchangeable with what is advertised as 1/2 in hose. Note: 1/2 in tubing typically reflects ID, not OD but it depends on the application. If it is aquarium tubing, it means ID which is 13mm.
I drilled my holes with what looks to be a 1 1/2 in hole saw, which has grommets typically used on desks. The hole size with the grommet is 1 1/4 inch but my tubing is still slightly kinked. The whole should be much bigger for the OP. Unless some really good S bend is used, the holes are too small, even if the tubing is smaller.
I would find the appropriate size grommet and cut elongated holes. I would then use something like this, but in the size that fits your application, I am just using this as an example of the type of grommet I would personally use: https://www.amazon.com/Large-Plastic...1116979&sr=8-6
If your stand is real wood and solid wood, you don't need the grommet if you can match the stain or paint, but I still think it looks better with it.
I would not use smaller tubing in general, and in this situation, it's a pretty easy fix. I imagine these holes are not for canister filters but airlines.