It seems I always have to add more powdered sugar than the recipe calls for. I also make sure I re-wash my tips with some white vinegar to make sure there isn't any grease in there that may break down the royal. And I usually use the parchment cones for the same reason.
Just some FYI (and if you know this already, I apologize in advance), but you don't have to make flowers from RI. I use BC for everything. Never use royal on anything cake. Never. Let BC flowers air dry (do not freeze ... AIR DRY!) overnight and they can practically be tossed across the room to the decorator to put on the cake! 
I use this RI recipe:
1 tbsp of meri white
45ml water
1/2 icing sugar (250g)
mix meri white and water together until dissolved. Add icing sugar gradually, and mix until stands up in soft peaks and is a bright white colur.
If you dont mix it enough it will have a yellowish tinge and wont be strong enough.
You probly will have to add a bit extra icing sugar, I allways do.
Lou
allow RI flowers a couple of days to dry out completely if you want to store them for future use. If not, you can usually use them fairly quickly. (when I have leftover RI from something, I make flowers and then store them away. When I need a quick decoration for a cookie, cupcake or cake, I just pull my box out of RI flowers and pick something. A real time saver.)
Quote by @%username% on %date%
%body%