SkipD wrote:
The 70-200 f2.8 L IS with the Extender 1.4X II attached (with lens caps attached to both ends and hood attached but reversed) is almost exactly 9-1/2" long and 4-3/8" maximum diameter (at the hood). Without the hood, maximum diameter is approximately 3-1/2".
These dimensions do not include the tripod mount. If you have space for the hood, then the tripod mount isn't a problem. If you're trying to stuff the lens into minimum space, you might want to store the tripod mount separately.
No small bag that I have seen is going to give you space for the diameter of this and the other f2.8 Canon zooms with their hoods on (either reversed or in normal positions). I have the Lowepro Stealth Reporter 650 AW, and it handles the three big zooms that I have (16-35 f2.8, 24-70 f2.8, and 70-200 f2.8 IS) plus a 20D/grip attached to any one of the lenses. There is room for a flash unit, meter, cleaning equipment, and a myriad of small accessories. It's a shoulder bag that allows all the lenses to be stuffed in from the top without having to lift anything out of the way. All the lenses wear their hoods. The 70-200 is the only lens that I have to reverse the hood on when stuffing it into the bag.
The 650AW is indeed an excellent bag...
In one configuration, I carry my 70-200mm f/2.8L IS (hood reversed) connected to a 1-series body, a 300mm f/2.8L (hood reversed), 580EX + CPE2, 28-70mm f/2.8L (hood reversed), 1.4x extender, 2x extender, 15mm f/2.8, two spare NP-E3 batteries, Variosix F light meter, rain cover, lightweight coat, notebook and pens, large blower, lens cloth, bar towel, chamois leather, 20 AA rechargeables, business cards, memory card wallet... I think that's the lot.
I also add one or two 60AW pouches to the bag if required to carry an additional body and any other accessories (e.g. spare flash).
Don't forget there are also two rain/dust covers built into the bag itself.
Getting back on topic, Skip is spot on with the dimensions of the lens/extender combo 
---- Gavin