The pre-eminent work on this subject was done 67 years ago - Preservation and Storage of Sound Recordings (Lemcoe, Picket, 1959). They analyzed 10deg off vertical (80deg) based on storage at 80F without being moved for 20-yrs with little effect and they tested under the same 10deg from vertical at temperature of 110°F for 1000 hours, three discs were placed in the chamber at 10° off vertical at 110° F for 1000 hours. See discussion beginning about page 35. Short term (<20 years) 20deg off vertical (70deg) should have little effect.

