These charge pump type voltage converters are really only suited to very low power.
If you want to deal with amps then you will be much better off using a conventional boost converter with an inductor as the energy store.
If you just want a 2:1 voltage change then a forward converter using a centre tapped choke and a pair of mosfets is likely to be the most efficient way.
I had a diagram on the old computer but it didn't get transfered to this one.
If you are not worried about the ultimate efficiency you can use a pair of bipolar transistors and a feedback winding and make it self oscillating.
Flux