h1b amendment - no client letter - emergency travel

[h1b129]

After researching through this forums, found several cases of VISA stamping resulting in 221g.

Feel this forum is the right place to get advice.

My case:

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Work for a Desi company in EVC model.

Am in 8th year h1b. Got H1b transferred/extended to employerB in 2011, got it till 2013(based on approved i140 from old employerA).

My passport has old VISA(employerA) expired in 2010.

I have a urgent travel plans to INDIA. Since my visa has expired I have to get it stamped.

I have changed clients after filing H1b petition. Have new LCA for new client address.

Note:Its against client policy to give client letter, wont be able to it.

1)Should I go to Canada/Mexico where stamping has relatively higher success rate?

a)Any one had VISA stamped successfully recently without h1b amendment after client change? Please share details

b)Any one had had VISA stamped successfully WITHOUT CLIENT LETTER? Please share details

2)Will I be able to get appointments in September last week time frame?

3)How risky is it to go for stamping in India(Chennai/Hyderabad) in above scenario?

Seniors, experts please advice.