UPDATE - I have changed this recipe! INSTEAD of Crisco shortening use Hi-Ratio shortening and you can now use the entire amount of meringue instead of disgarding. Now it holds up better to heat due to the hi-ratio shortening. Use equal amounts of butter to shortening (1lb. each for one batch of icing.) It is not as soft using the hi-ratio so the "learning curve" on using this icing is no longer necessary. It behaves like most buttercreams and holds up well to piping.
When you say "you can now use the entire amount of meringue instead of disgarding" are you referring to the entire egg? Also what is Hi-ratio shortening? is this a brand? I"m looking for a recipe for buttercream that will hold up in hot weather. Any advise would be greatly appreciated.