What size hose are you using? I normally use a 3/8 fuel line to do my siphoning. I have it hooked up to an old fuel pump. Does a nice quick job. Sometimes a piece of garden hose will work better becuase it's a little stiffer and easier to push down in the tank.

A lot of times I'll skip the siphoning and just place a floor jack under the tank and let it down that way. It helps if there's and extra person to help steady the tank as you lower it.