Ha ha, I'm here, since you asked for the experts...The ASME VIII code stipulates that the U-stamped vessels can use only the materials listed in the ASME II Table D and the materials recognised by the ASME as equivalent (refer to some code cases). And yes, the saddle support materials have to be also certified for compliance with the ASME code. However, why would you U stamp a vessel in Pakistan or anywhere else outside USA, when you only have to get certification of compliance with ASME VIII from the third party review and inspection authority (DNV, UL, LLoyds, etc..) for your insurance...If you can do away with the U stamp, you might use the material fabricatior to certify for you the equivalency to an ASME material and get the third party inspection approval to use the material on the mentioned vessel and be done with it. The stamp is only good for headaches and is anyway useless outside USA. Also, the U-stamp is not even recognised in many parts of USA, notably TEXAS and other states...
cheers,
gr2vessels