Yup, zero doubt the engine was mounted inverted. Not sure how legal it would be for OTS contests, but with your original for documentation, perhaps it would be allowed. OTS rules are pretty specific and exclusive by nature. I think that would be an awesome looking Barnstormer, and encourage you to replicate it with the inverted engine.
My Dad flew his Barnstormer with an O&R .29, and tore the wings off it twice (in the air!), so be sure to sheet the wing center full width and do NOT leave the access hole for bellcrank inspection. I'd also put in a 4" bellcrank and reduce or eliminate all the rudder offset.

Steve