While velcro is a great option, I highly recommend and adjustment your method. The gap between the foam and shell created by the Velcro will result in condensation on the interior of the shell. It will also greatly reduce the efficacy of the insulation. For an air barrier to work it needs to be a %100 sealed air barrier. With your setup the air can find all the gaps between foam panels and circulate behind them.
I would recommend a few strips of Velcro per panel running the full length of the panel edge in parallel with the curvature. Then between the strips of Velcro (on the foam panel) glue an additional 1/8″ of closed cell foam. This will seal up any air gap assuming your Velcro is <= 1/8″ thick.