I like the control I get with a hacksaw blade held in gloved hands. Not a lot of dust as with a Dremel or other power tools and excellent control, so no mistakes. You can cut a couple of layers of glass with ease and follow the cut line, go at a cut speed that provides the least risk of cutting an area you didn't want cut. Use some coarse sand paper to finish off the edge.
Steve Briggs. RV9, G3x, G5, VPX, GTN625, PMags, A&P, IA, ATP-CFII