Carl,
If the EOR says you can follow D1.1, you can certainly use it. The EOR has the authority to invoke whatever criteria he/she deems necessary on a project. However, if you have legitimite concerns, you need to convey those concerns to the EOR. The fact of the matter is this: An EOR isn't a supreme, know all being, and a fabricator has a practical knowledge that is not taught in college which he gains on his day to day experiences. An EOR can benefit from this knowledge, so feedback from the fabricator is a very important part of the process. A project is a team effort between design, fabrication, and erection, and everybody's input is needed to make it a success.