From another thread I had started, there was a bit of discussion concerning SMC and additional disabilities. Here is a BVA case that shows once a Veteran is SMC eligible, any additional disability ratings ARE NOT combined....
At the outset, the Veteran has been awarded entitlement to
TDIU, effective June 10, 2002, primarily based upon his
service-connected acquired psychiatric disorder. Effective
June 10, 2002, the Veteran also met the criteria of having
additional service-connected disability independently rating
at 60 percent or more (left knee degenerative joint disease
rated as 30 percent, left knee subluxation rated as 10
percent, and left common peroneal nerve injury rated as 20
percent). As such, the record establishes the Veteran's
entitlement to SMC benefits under 38 U.S.C.A. § 1114(s)
effective June 10, 2002.