The delay is pretty flexible. I'd say 2 seconds to somewhere between 5-7 seconds for a skillchain. To solo renkei as a ranger, what multi hit WS are you going to start with? Barrage at best is going to return 56% tp so you need to make 46% somewhere else. I'm still one level from sidewinder, but I do believe it does 4x damage, not 4x separate tp hits (can't find any English sites with good info, but the kanji descriptions seem to indicate this). Rampage is a 5x axe WS which may give you 46% tp, but I doubt it. Even if you managed to get every hit, you'd be counting on rapid shot to kick in on the barrage to make it in time.
This is all pure speculation. If anyone has ever seen it done, I'd be interested to know.
Ras <Lost Anarchy>
Human Priest, Ner'Zhul