I am wondering what I can add to my bc to make it stand up to warm a area ? Do I want to not use butter or maybe 1/2 the amount? Its for a wedding cake. maybe powdered egg whites?

Sugar Shack and Indydebi's recipes are more stable for outside events (100% shortning) but there is nothing made of sugar that will hold up in direct sun for too long. Sugar melts, just the nature of the beast.

If it is going to be in the shade you will have more display time (as long as you don't have heat sensative fillings) but if at all possible, keep the cake in an a/c building until absolutely necessary.

I have historically used a 1/2 butter, 1/2 shortning recipe w/ meringue powder added and still had the icing melt due to heat. Like sugar, butter melts.

HTH.

I used Indydebi's recipe last weekend (90 degrees out) and it held up good. One layer of the layer started sucking up the frosting and showing through - I'm not sure if that was something I did or if it was where the sun was hitting the cake. It sat out from 4:30 pm to 6:30 pm. HTH!