… a do-it-yourself tool for holding the piston when fitting the cylinders.

Anyone who has ever fitted / mounted a cylinder on an installed Rotax and not fixed the piston would probably have preferred not to do this.
The piston wobbles and the cylinder cannot be „threaded on“ very well.

There is now a simple DIY tool to overcome this hurdle. And it looks like this:

Two square plastic rods and a screw with nut….

The dimensions of the rods are 15 x 15 x 150 mm.
A 6.5 mm hole at each end, both connected with a 6 mm screw, approx. 65-70 mm long.

The advantage is that the tool can be used on any cylinder to be fitted as it is so flexible.
In practice, it looks like this:

Good luck with that….