I did that for a while you will get good results only problem is you will have to use fairly high flash settings and most speedlights have shorter duration the lower you can set it which helps stop movement.
This DIY Snoot directs the light to a specific area. On macro's, a lot of the time you need a strong light source because you use a smaller F-stop for better depth of field. I guess it depends on the size of the subject.
Great idea! If you own a Lite-Scoop it also is very effective for macro photography. Not as cheap as a Pringles can . . .but if you already have one . . give it a try. This is not like a bounce card that lets most of the light go in the direction of the flash head . . . but instead diverts over 80% of the light forward from the Lite-Scoop.
A lot or women would agree, a little bigger is always nicer. However, as men would respond to them, its not how big it is that matters, but how you use it.