I have a Dexcom for trial again, and I’m experimenting a bit today. So far, I have an incredibly succesful D day today. I had half a pie of pizza for lunch (bolused 4 units) and two portions of ice cream at evening (bolused 3 u). I haven’t had any spikes - I bolused 20 minutes in advance, that seems to do the trick for me. BG in range the whole day, without excessive fluctuations. If only every day was like today 
Just for the record - I dont eat these D-killer meals very often. I just wanted to see my BG reaction to these in realtime.