It's *really* easy for fast riders to invite people assuming that well, their group don't go that fast, really... so I htink I would go, but with a strategy if it's apparent that they get out and do 19+ in their paceline. Though, if you can go 15 by yourself, if you activate your hormones and really focus on round pedal strokes, you may totally surprise yourself. DOn't ask yourself whether you "can" or not... when it seems like you won't be able to keep up say "okay, but I will for another mile or two..." and you just might find a rhythm.

I would, however, know my way back and if I wanted to drop off I'd say "I know my way back, y'all keep goin!"

(I'm coming back from a posted no drop ride that just happened to have strong enough riders that didn't get dropped, but we were doing the posted speeds -- well, after the initial sprint, we did for a little while - into the wind... let's just say I hope some of us with a true no-drop spirit are there when somebody tries to move up from level one to level 2, because the ride leader sort of forgets hers sometimes. )