When dealing with tandems in general, it's best to look at component manufacturer specifications as guidelines not absolutes.

Moreover, if you ever ask for anything in writing or via Email, don't expect to get much more than a restatement of the approved specifications and uses. The latter is why I tend to call and search out technicians who are willing to have a practical and throughful discussion that "can't be used in a court against them".

Frankly, if all of the various specifications and incompatibility issues were real and endorsements for use on tandems were required, you'd be hard pressed to find enough parts to build a tandem.

Just my .02.