to answer both your questions when i did my 50g cutout i bought this
http://i998.photobucket.com/albums/a...5_XB-LF1_3.jpg

then i used a guide with my mastercraft hi rev dremel tool not your regular dremel but large,r and slowly cut out my notch. i planned to do the same idea with the 2x2 pane in hopes the vibration didnt crack it. i would draw out the curve i wanted as to not have 90 degree cut and follow the curves free hand. or make a jig to make them uni,on. and viola a one piece euro brace x 2 one for each side

I would get a small hole bit and drill each corner then join them

^^plus one. I've done this before. Drilled 4 holes and joined them. This was done while the large brace was on the tank.

i like drilling the 4 holes idea just have to buy a bit for that i will add it to mylist of things to buy.