I have a Duetto II on order, and will make these mods as well.

Still debating between the Mentor 270.4 and the VBM arc style handles. I found a couple places that sell both.

I also plan to insulate the top of the steam boiler as well. Any issues with insulation on top of the boiler? Anything I need to avoid or be aware of? Also thinking of using foam insulation sheet to make a divide between brew boiler area and the Gicar unit just to limit heat to this area, don't know if it will be worthwhile but I have plenty of insulation available.

While steam could condense on the board I would be more worried about the OP valve spraying water inside the case and making sure that water could not reach the controller.
But remember that it needs to still be able to draw heat away from some higher current parts. So airflow is still needed.

-Cecil