If it's severely overgrown, I'd think you'd be fine. Sure, a few growing points might get broken in the process but if it's that overgrown, you probably won't miss them. Up until this year, I would have probably been about as scared as you to divide said lotus. But I just (2 weeks ago) divided two lotus that had been growing uninterrupted for about 5 years now and they had also started peeking up little unfurled leaves. It all went fine and I ended up just breaking a few growth tips. Even with those being broken, each lotus still yeilded about 30 tubers each. Basically I took it slow, unwound the entire tuber mass into one long strand, and then made sure that each snip of the scissors left me with 4 or so unbroken growth tips per division. Hope this has helped! I think many people, including myself, think that lotus are a lot more fragile than they really are.
