Is this an ARF or kit 4-Star 60? If it is a kit then just take a look at the plans. I've never built the 60 size but the 40 has downthrust if I remember right? It has been a while.

You might ask over in the kt building forum, I'm sure someone is working on one or has plans to look at.

You can definitely just epoxy in a new firewall without the interlocking tabs and use some tri-stock. You can also pin it with some hardwood dowels and it will be very, very secure.

However you set up the engine thrust you can always adjust it after flying like CGretired mentioned.