Thanks for all the help, much appreciated!
Done some measurements on the top and lower pin’s: they match the category 1 sizes mentioned in bcp’s table (top is 19mm=3/4inch, bottom is 21mm, about 7/8 inch). So the pins indicate that the tiller is a cat 1, as is the 2305 (limited is no issue, since it can be lifted high enough).
Strange thing is that the spacing of the tiller is not category 1, although advertised as cat 1 and 2…..
Mounting the arms on the outside does not work: 1) the pins that come with the tiller are too short to do this, and 2) the strange green handles are in the way.
I tried to use the JD bar (you can see it lying on top of the tiller) that is used to lock the arms when not in use, but because of the handles I cannot move the arm over bar.
So alternative 1 is remove the 2 handles (don’t know what they are for), and use the JD bar, and some spacers that came with the tiller to install the arms on the outside (although my girlfriend doesn’t like me sawing some parts of the new tiller ;-),
Alternative 2 is like Dutch445 suggests to drill additional holes to attach the turnbuckles, so they can ‘fix’ the tiller.
Alternative 3 is to attach additional chains to ‘fix’ the tiller like joshuabardwell suggest (if I understand correctly).
At the moment alternative 1 seems the most obvious to me, also it increases the arm spacing, and thus stability.
Alternative 4 is to have the JD dealer do some welding and increase the arm distance. Only thing is that it’s a nice jobs to get the 100+ kilo tiller to the dealer….
Thanks again for all your help and suggestions. I will let you know how this is resolved.

