Guys there are several ways to deal with the exhaust exit facing the wrong way...a couple ideas have been posted recently, I have some more to offer:

Mike Pastro designed a few pushers 10 years or so ago, and the way he overcame the back pressure issue was to attach a small tab of brass strip on the front edge of the exhaust nozzle..sort of a wind deflector...simple and it worked (I own one ( or rather what is left of it..of his prototypes). Simply drill a hole and use a sheet metal screw to attach the brass strip to the exhaust outlet

Mousse can mufflers were the rage a few years ago....for a few bucks you can build one to replace the back end of your current muffler, but have your exhaust come out at an angle facing the rear of the plane. 2-56 or 4-40 fully threaded rod would hold the whole works together..

There are at least 2 off the shelf hardware items that can be purchased at a hobby shop that will reverse the exhaust flow.. I want to check them out first, and it it looks like it will work, I will post the part numbers.

The hobbico deflector is not a real good solution, because it is flexible and vibrates and buffets in the air, as well as gets oil underneath with the result that it will eventually wiggle loose (BTDT ! )