The A32 Vixxen (and A22 Foxbat) can be freely side-slipped with or without flap. Pilots should read the Pilot Operating Handbook (POH) carefully, as the information on side-slipping speeds and bank angle limit is all there. In summary for the A32 Vixxen: the limit for full control deflection is 81 knots – this is the top speed limit for side slipping with no flap. The flap limiting speed is 79 knots and this is the top speed limit for side slipping with flap. Technically, there is no bottom speed limit for side slipping but be strongly aware of stalling at slow speeds with large control surface deflections. Stall speeds will be higher than in normal straight & level flight! Finally, the maximum bank angle for slips is 15 degrees.
Personally, my preference for side slipping speed is somewhere between 50 and 65 knots, with or without flap. Everything seems more comfortable and controllable at these speeds, which are well above the stall and don’t stress the airframe to its maximum limits.
Hope that’s helpful!