I was at Lowes tonight and found an insulation thats an extruded foam of sorts,,and its realllll flexible,,one inch has an R-value of over 4,,a 4x8 sheet is just under 7 bucks for 3/4" might be just the ticket for those tight bends on the top,,,it also is skinned on both sides which gives it a good bit of stability,,,,interesting stuff,,,,
chip