This was the panel before I started
Working out the correct positioning for the porthole
First, centre hole drilled, then 4 more at the hour, half & quarter hour positions, then 4 quarter arcs cut with a jig-saw. There was a 285mm diameter hole in the side!
With fibre-glass insulation removed and the porthole in place
The finished job, sealed with 'Sika-flex' and all of the screw slots aligned! Glass in.
The finished job - I was really chuffed.
Now all I have to do is sort out the inside. A number of the wall tiles need to be shaped to fit the porthole liner. It is great to have light and ventilation in the loo!