Vertical Batten Pool Fence - Thoughts

The hole will need to be drilled 1 or 2mm bigger not smaller, as you will never get what looks to be copper pipe through the opening.
You would then need to fix a screw from the back through the copper pipe, glue won't work, and wouldn't pass code.

Sounds like you have never attempted something like this before, so here's some advice.

The copper pipe will need something else inside it to give it strength, copper pipe on it's own could be too flexible and easily bent out of shape.
You will need a drill press for the holes, this will ensure the holes are drilled perfectly square and all in the same position (achievable by a simple jig).

It looks like 35x90 blackbutt they have used, not sure if you have see the price of timber, and lack of availability, but it will cost a fortune and you might not be able to even source it at the moment.
eg: regular run of the mill 35 x 90 dressed hardwood is around $17 / lm, 90 x 45 blakbutt around $28 /lm