Great balanced article and advice. Should be useful for both beginners and others pushing things.
I really DON'T care to get involved typical overzealous debate and spamming match it could cause.
Enjoy,
www.supconnect.com/opinion/tipping-point-when-is-your-sup-too-small
I think the main thing people need to realize is that you shouldn't be able to downsize and just be able to paddle and surf easily right away. It's a worthwhile learning curve and you have to go through it. Your new "short" sup should absolutely frustrate you some in the beginning... trust me that learning phase doesn't last too long. Every time I've gone smaller it was a struggle, then about 3 weeks later you feel totally used to it. People need to get away from the instant gratification thinking. Just my two cents!
Interesting link and a good read.
I know the board I am riding is to small when my takeoffs are getting ridiculously late and I keep running out of water with long waits between ride able waves.
A three board quiver, 9.5, 10.6 and 14footer covers the 2km of coastline I pickover. 
The article quite informative and to the point, but I would be a bit more precise. After a certain level of experience, you should distinguish the 3 aspects: length, width, volume.
The drawbacks, for me:
Too short is easily compensated by technique and wave observation, but harder with fast waves.
Too narrow can be hell, and will test your reflexes, and, let's face it, is really more difficult to manage with age, and chop.
Too low volume is not so hard (if not too narrow), but extremely more tiring and paddle like a sea anchor.
The advantages:
Short allows to fit insane curves in small faces and tight corners
Narrow allows insane rail surfing (no latency in rail-to-rail) in powerful conditions, as shown in the last world cup at sunset
Low volume is insanely more manageable in hollow waves
So by balancing the drawbacks/advantages with the conditions of the day (and your mood), you can often get (a bit) of the advantages without (much) of the drawbacks
This is a very good topic indeed .
Many parameters surrounding all to stand up paddling 's purposes on a surfboard had been described ; Excepted one which is the ratio of volume / surface of the board and how their distribution is organized. That parameter of ratio area/ buoyancy is the key to do the most functional and fun design .
To explain shortly : there is more stability to stand up paddling on a piece of plywood rather than standing on a rounded buoyant .As well you might standup longer on a piece of plywood before sinking than the buoyant still floating at the water level. In last that's more fun to surf riding a plank shaped as a skimboard. 
Nowadays there is more too big SUP rather than too small SUP. The prime question to be asked would be : When do your SUP is too big and what is the real satisfaction in surfing even standing up paddling on a surfboard.
To my opinion there is no satisfaction if no challenge does exist 
I find it is good to have a board a little to small and a board that's just right. The board that is "just right" should feel so intuitively. The board that is a little too small eventually becomes the correct size as skill level increases and muscles adjust. Then drop down again.
I think leaving time for the muscles to adjust is really important. In saying that, I am learning more stretches and more ways to improve technique all the time which helps with dropping a bit of volume.
Select to expand quoteKami said..
This is a very good topic indeed .
Many parameters surrounding all to stand up paddling 's purposes on a surfboard had been described ; Excepted one which is the ratio of volume / surface of the board and how their distribution is organized. That parameter of ratio area/ buoyancy is the key to do the most functional and fun design .
To explain shortly : there is more stability to stand up paddling on a piece of plywood rather than standing on a rounded buoyant .As well you might standup longer on a piece of plywood before sinking than the buoyant still floating at the water level. In last that's more fun to surf riding a plank shaped as a skimboard.
Nowadays there is more too big SUP rather than too small SUP. The prime question to be asked would be : When do your SUP is too big and what is the real satisfaction in surfing even standing up paddling on a surfboard.
To my opinion there is no satisfaction if no challenge does exist
+1 Nicely put Kami
Select to expand quotechrisrum said...
I find it is good to have a board a little to small and a board that's just right. The board that is "just right" should feel so intuitively. The board that is a little too small eventually becomes the correct size as skill level increases and muscles adjust. Then drop down again.
I think leaving time for the muscles to adjust is really important. In saying that, I am learning more stretches and more ways to improve technique all the time which helps with dropping a bit of volume.
This has pretty much been the way I have done it even on prones. Longer board to develop power and trim then a performance board for tight aggressive surfing. It's rewarding to play the boards off against each other.
Thanks for all the thoughtful responses.
I love that debate make me remember when I had to shape my next prone board while demoing my last one
SUP is such a renewal in many surfing aspects. 
