I was shifting my 105 5800 both front and back at virtually the same time when dropping to the small front. It handled it beautifully, IMO. Frequently it took two sometimes three smaller cogs in the back to achieve the correct ratio for my cadence.

Since in both cases front and back you are going to a smaller cog, you don't have to let up on the power quite as much as when shiftting to bigger cogs. At least I didn't think I did.

That bike has an 11-32 with 52/36.