Do they stack? The rules say that once you have picked up an object via SS, your next close combat attack must use the item...

Also, whats the rule concerning taxi'ing another flying character whos holding an object...(realistically they would just be pushing/pulling the hovering character)....

No.SS cannot be used with CCE and vice versa.The only way to taxi someone who is holding an object is by TK.

As the rules are now, when you are using Super-Strength to lift an object you are using your Super-Strength power. CCE cannot be used to give +2 damage when you are using other super-powers (except ProbControl). So they do not stack.

Also as four_winds said, you can't taxi a figure who's also holding an object (though a flyer with SS could pick up an object and a figure seperately).

Actually, lifting the object isn't considered using Superstrength, althought it should. If that were the case, then if you were holding an object you would be unable to do an RCE ranged attack as well, which is the way it should be. The reason is that in a close combat, the object must be used and the using of the object in combat requires the use of Superstrength which cannot be used W/ CCE. Nitpicking I suppose but It is relevant when considered w/ RCE.