Pity about the leaks, someone posted a video of using epoxy and the idea was to pour a thin layer first, this would both find and plug leaks for the final layer.
The 7mm hole works great, anyway it looks like a great job, nice and flat and clear. Remember to give it plenty of time before bolting the rails on, you don't want it compressing slighty like mine did after 3 days.
It's a great feeling when you've passed this stage of the construction, it's like getting past the foundations when building a house and the epoxy is the damp course.