[Panzermann]

@Dougl - My initial thought would be to use a fine tooth-hole saw. Lay the panel on a block of wood and align the outer edge of the hole saw and the semi-circle marking. Clean up the edge of the cut-out with some wet and dry sand paper.
View attachment 119052

If you used this method, you would want to screw the part to the wood using some self tapping screws around the periphery of the waste piece.

 

[Panzermann]

You could always do it like the shop would - a pair of curved snips. Rough enough is good enough. 😄

 

[Panzermann]

You could engage the Cookie Monster …

 

[Panzermann]

That could work. When I mentioned chainsaw, I actually had one of these in mind ...

Lancelot Woodcarving Tool - Lee Valley Tools

www.leevalley.com

That attachment is designed for wood carving rather than precision cutting a circle, especially in thin plastic.

It’s also one of the more dangerous wood carving power tool attachments.

 

[Panzermann]

The cutting task is rather minor, so I’d avoid power tools. A coping saw to cut close to the line then emery paper wrapped around a tubular surface not too much smaller than the desired radius (any appropriately sized household item) to finish up to the line would be my approach. Gently, gently.

 

[Panzermann]

Seems like the collective sense of humour has evaporated.

I didn’t know whether to laugh or cringe in fear that someone might take you seriously