[Gordon Steadman]

With the Dremel Kev, I just go slowly as I don't want to go through the sides but I will go all the way through the bottom

You're a lucky man. I've been through loads of Dremels (regular burn out or switch failure) until I saw the light and bought a cheap Chinese knock off that has been perfectly reliable and has a huge selection of cutters. (Probably made in the same factory!) Dremel tools are stupidly expensive and even balsa will blunt them if they are used regularly.

I drill out the bottom and the use the rotary to join the dots and thickness the edges. Good to see your work. The metalwork is superb.