Cool! I've been using the anti-slip mats available in automotive and furniture shops. They work great both with joysticks and pedals and can be washed if they start to get slippery because of dirt.
As for suction cups, I don't like the extra wobbling they add to the base. A bunch of mini suction cups instead of four large ones in the corners sounds a little more stable but then again, how much soft padding does the actual mat and Velcro add?