Couldn't seem to get this working in the right thread,but here goes.....
This is the heiland template.
This was found by someone else,no idea where the original site is,I can't seem to find it,lmk if you know!
Print out at 6"x6" for scale.
Buy a chromed vacuum cleaner spare tube.
Beg,borrow,steal a dremel.............
Cut out holes in template.
Attach template,and cut out oval holes.
As you will get at least 3/4 goes at a standard vac. tube,by the third time,you'll have got it spot-on.
Can't seem to load the image,so look here.