I agree with Laegwen, I don't like transfer because there's more possibility of colour bleeding. I think colour bleeding is very likely to happen when I put RI tranfser onto wet flooded base.
Piping white outlines and the fill with red seems a little risky to me. I think red icing needs to be "not too runny" and I would try to dry the red icing quickly using a food dryer or fan. Piping white outlines afterward is safer, but I think it looks better to pipe outlines and then fill the space with red.