I live in Tucson - same weather. Have never had a problem with USPS (recommend Priority however) as long as the following steps are taken:
1. Use an LP media mailer (not 2 pieces of cardboard taped together!)
2. Take the record out of the cardboard album sleeve and lay it on top of the album cover (in its inner sleeve of course.) Place an additional piece of corrugated cardboard on the top and bottom of the "sandwich", and for maximuim stiffness, remember to orient the corrugations of the upper and lower cardboard stiffeners at 90 deg. to one another.
3. Crease the edges of the media mailer to fit the thickness of the record "sandwich" and tape securely with mylar packing tape (mylar won't stretch with heat.)
The name of the game is making the whole assembly stiff, and the thickness of the mailer box to just match the thickness of the "album sandwich" inside.
.
1. Use an LP media mailer (not 2 pieces of cardboard taped together!)
2. Take the record out of the cardboard album sleeve and lay it on top of the album cover (in its inner sleeve of course.) Place an additional piece of corrugated cardboard on the top and bottom of the "sandwich", and for maximuim stiffness, remember to orient the corrugations of the upper and lower cardboard stiffeners at 90 deg. to one another.
3. Crease the edges of the media mailer to fit the thickness of the record "sandwich" and tape securely with mylar packing tape (mylar won't stretch with heat.)
The name of the game is making the whole assembly stiff, and the thickness of the mailer box to just match the thickness of the "album sandwich" inside.
.