[jacquesm]

The duct tape insulation at the bottom of the heat sink is a pretty bad idea, better use some mica and/or some stand-offs for this. Duct tape has some insulating properties but simply isn't made for this application and given the voltages in play I would definitely not use it.

Otherwise: this is a neat little inverter, it's basically a minor variation on the application note for the driver which does all of the heavy (PWM) lifting.

If you can't get transformers that are large enough you can put several in parallel using a small series resistance if the output voltage isn't exactly right (usually a case of one winding too many or too little on the secondary (now primary)).

Be careful too with those HV caps, those can hold charge for much longer than you might think when they are out-of-circuit. If you can use a higher voltage (48V preferred), and go for a transformerless design because that's so much nicer to haul around (besides being much cheaper).