I would probably add an extra brace from the ladder back to the tree trunk. You just don't want it folding up somewhere in the middle and I think that would be the risk you would run.
If as has been said, they are locked/pinned together and you brace it adequately, shouldn't have any problems.
The only thing that you may want to think about is how that will change your climbing angle, not that it will make a lot of difference, but to keep the platform level, your ladder will have to be much more vertical.
You'll definitely want to brace it more. What height is it now? You gotta be really careful with things like this.... You might get away with 5 feet, but no way would I try 10 feet.
I have added 1 ladder section to a 15 ft. 2 man stand before just to get it up a little bit. I bought the correct ladder section from the manufacturer and properly braced it and it worked very well. No problem whatsover except some dirtbag came and stole that stand about 6 months after I put it up.
I have added a ladder section onto on of my 2 mans. Just make sure you get an extra brace for the ladder. Works great just be careful..
I have added a fourth section to increase the height of my 15-foot ladder stand several times. I move the brace up one section and it is fine. I would not suggest add a full ten feet without adding a second brace, but I haven't tried it. Just the thought of putting the thing up scares me.
I have made extensions for all the ladder stands I use. I make them out of 1" black pipe and use couplings to insert the existing ladder feel. Weld it all up and paint it and it is more sturdy than the material the stand is made of. I tie the ladder to the tree in the ladder section 3 places in 21'. I hate rattling ladder stands so I tend to over do the braces to the tree.
