We have a bait board that connects to the gunnels  just inside the bimmini clears. Out of the wind and rain etc.
 On that we put a std colmans 2 burner lpg  primus with a hot plate.
There is more than enough air gap underneath to not effect the plastic bait board.
Between the back of the bait board.. between the bimmini clear and frame, sits on the top of the gunnel,  I have a small sheet of acrylic off cut  that gets warm, and keeps heat off the clear.

Only difficulty (if could be called that, was had to put a brace leg ( length of electrical conduit) to support part of the weight when have the kettle  and or cast iron plate and cooking.

We run it off a small 2kg lpg bottle.

As someone that survived a fuel boat explosion can only advise you to think very carefully before operating any form of flame cooker aboard no matter how minimal the risk.

Steps wrote: That sort of thing is caused by leaks, not checking connections, bad storage etc. and assuming all is good... Out of interest petrol fumes are far more likely to ignite than lpg due to the air/ fuel ratios needed to do so, and the band in which they do.  The danger is in ppl rather than the tools.

And room for dishing up plates each side

We used to overnight in a 5m open boat a few times a year. I never gave too much thought to the danger of petrol fumes....... I was always  more concerned about the lpg . Always double checking  that the cylinder was turned off when not cooking, especially when going to sleep.