Okay, so, you're probably not going to believe this, but I don't think Falco has an actual chaingrab on ROB. I did the walking CG and the running CG, buffering, etc., but ROB could usually just airdodge after the first DThrow, fresh, 0%.
Taken from the Falco board's CG Breakdown thread:
ROB
Walking Chaingrab : 0-18% (2 times)
Running Chaingrab : 0-18 % (2 times)
Counters : Jump (18%); Fair (?? %)
I don't know. I'm no Falco main, I might've done something imperfect when chaingrabbing. But I suggest you take the Falco board's word for it. Two grabs seems right given decay, knockback, and hitstun. Also keep in mind that the thread stated that the CG data was gathered in training mode, which has no decay, but it doesn't give moves the "fresh" bonus either. I tested in an actual match though, refreshing DThrow as neccessary and SDing to put ROB back to 0% after each trial.
Post this in the thread if you want, or I could if that's what you'd like.