The inside of my GIS is fully varnished, so it has also varnished floorpanels.
It appears that these panels are too slippery to be comfortable especially when wet in more heavy sailing circumstances.
This is also due to the fact that a GIS can handle greater angles of heeling in gusts and f.e. when you are roll-tacking.
I decides to make non-slip area's in a simple inexpensive way; using fine sand ( so-called "birds-sand") and varnish.
First step is to sand the floorpanels and to mask the area's that should not have a non-slip surface.
The main area's that needs a non-slip surface is in the back of the boat, where you do most of your sailing. But I also made a non-slip area in the front part.