was planning this and test with few similar option before but never got any good result. but then decide to share this even I feel this still having problem with my setup
why am I building a bigger diffuser
1. larger light size
2. softer light
3. my long MACRO len (SIGMA150) need better and larger diffuser (I need something work for both of my MP-E65 & SIGMA150)
so my testing make up of
1. pop up flash diffuser

2. styro foam bowl& Kitchen towel paper

3. final setup


sample output .. (sorry trying to get back the original setup but the beetle flew off)


(minimum PP done on above pictures)
based on last picture show above (my large diffuser is from right from my len and the small one is on left) overall the light diffuser better than my previous one (I personal feel)
but it create bad shadow after 3:1 which mean I lost 4-5:1 while using my MPE , think this could be over size of my big diffuser ... will try to make it smaller next round