On the stretch play - If Guards are covered the owness isn't/shouldn't be on the tackles, it's on the Centre to work to the combo block with the OG to ultimately take over the block to allow Guards release - I've said a number of times before, when you have an athletic/aggressive centre like Pouncey who in effect can reach a 3 tech, you can do some significant damage with the stretch play.
However - the beauty of the ZBS, and in particular with the stretch, it's not just one play, it's two - it's an outside and an inside [with the cutback] run play.
The other aspect is, you can actually run outside stretch, with inside zone blocking - some of you might think what??? but, with alignment and package e.g 12 personnel - you could over load 2 TE's on one side, and with inside step/inside zone blocking scheme, could in fact run stretch blocking effectively. Case in point - Seattle did this well with either 12 or 11 personnel.
So it really shouldn't depend on the fronts you see in what you can do... yes, it impacts on alignments and footwork but that's the beauty of zone its about vision and you put the responsibility on the back to read the colour, so to your point about inside shade on OT's... by having that athletic OC who can take care of DT's, say in an under front and you are running stretch weak, i.e. towards the under... the OT really shouldn't have to rip the inside shade - I would fully expect him to have a clean release to the 80/90 backer - because with an inside shade, i.e. 4i or 3 tech, means you likely have 1tech DT with a 40 front or even 30 [i'm being generic with conventional scheme/wisdom to be clear] - which is Centres responsibility, which leaves the OG to take over the OT's inside shade [whatever tech you want to assign it]
Anyway, sorry... got carried away on that... my bad :)
