Do NOT add insulation to the oven! The microwave/convection oven vents heat inside the galley cabinet, and insulation would block the vents, causing the oven itself to overheat.
You might add insulation to the surfaces that get hottest inside the cabinet, but not to the oven itself. Prodex is probably your best bet for this, since it has maximum R-value for least bulk and will not use up all of the air space inside the cabinet that you need for appliance ventilation.
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