Hi Ogre, well done on the modification. The bees should be nice & cosy in there, summer AND winter. Another advantage is it wont break your back trying to lift it. Wall thickness like that is often used with native beehives because native bees have trouble regulating temperatures. Whereas honeybees are better at regulating the temp. because of their body mass.
Anything we can do to help the honeybees regulate the temp. can only be an improvement. I hope that stuff you got didn't break the bank:)