NOT TRUE!loongyh wrote:There's no way toner transfer can work on this.
I've made double sided toner transfer boards with SMD parts having 0.5mm pin spacing, which is more compact than what you did. The trick is to use a good toner transfer system such as the press-n-peel blue available from allelectronics.com I etched each side of the board separately protecting the reverse side with a layer of spray paint (removed later with mineral spirits). I drilled a few holes after etching the first side and used pins to align the second side transfer sheet while ironing it on. I got very good alignment between sides. I did have to use wires between sides as you can't home brew vias!