I'm a bit late to this, but I just stumbled across this page while searching for information about a particular architect, and I think the author "Howard, Elwell G." is probably him. If it is, his name was actually Howard George Elwell, and Mott Studios was not alone in butchering his name. Boxoffice Magazine did it, too, calling him "Howell Ewald." I unwittingly perpetuated the error on
a page at Cinema Treasures. Elwell designed a theater called the El Rancho in Victorville, California, which was opened in 1950. I just discovered that
the El Rancho was featured in the 1950-51 Theatre Catalog published by Jay Emanuel Publications, and the Catalog got his name right.
I haven't been able to find out much about him. Though he is mentioned in a lot of architecture periodicals found at Google Books and the Internet Archive, I haven't had time to look through them yet. He was active at least as early as 1916, and died in 1961. His listing in the AIA directory of 1956 had only his office address, 1200 W. Fifth St., Los Angeles, and no list of his works. A Google search on Howard G. Elwell turns up a few listings for houses in Pasadena and San Marino.
Hollywood Heritage had his 1959 Christian Science Church at 7107 Hollywood Boulevard on its
Endangered List in 2012. So far, that's all I've got, but judging from the few buildings I've seen photos of he kept up with the times. The theater in Victorville was clearly Midcentury, and the Hollywood church is very much of its time as well. The doctor's office is quintessential '30s modern. I'd look forward to learning more about Elwell. There might be some unknown masterpieces of his design rotting out there.