I have an inverted Saito 72 in a Decathlon and i want to cut a access hatch in the cowl for tuning i have a dremel tool but does anyone have any tips for this? I am going to hinge it and put an inner frame so the hatch wont close to far in and i will use a magnet to hold it closed. I am looking for a way to make i nice accurate cut maybe with a template.

I suggest buying the plastic cutting blade for the dremel tool. Mine cuts perfectly sharp edges with no melt. So your hatch door will fit right back into place.

Once the engine is adjusted you shouldn't need to mess with it enough to want to go through the work of fabricating a hatch. On my cowled glow powered airplanes I have a single 3/8" hole with a rubber grommet that is just big enough to get a pair of hemostats on the high speed needle. Although once set up I virtually never have to re visit.

The engine was tuned but I switched from 15% to 20% fuel so it needs a minor adjustment and in case I happen to use different % fuel in the future.

If you are going to cut a hatch, it helps to first put down masking tape, then draw the hatch outline. The tape helps keep the cut from wandering and the edges cleaner. If you go Speedracemntrixie's route, which is what I usually do, put a cut off allen head bolt in the end of the high speed needle (I think 2-56 fits) and secure with the set screw. Then all you need is a tiny hole for a 2-56 ball driver to fit through. Much less noticeable and the ball driver makes adjusting the needle much easier, particularly fine adjustments.

A small screw in the HSN and a hole to access it from works pretty well too. The LSN on a Saito doesn't usually need adjusting at all once it's set right to begin with.