Its very solid as-received - there isn't much that needs modification.

I originally powered my WM Miss America with an OS .70. With everything mounted the plane balanced perfectly on the first attempt. It was not necessary to add weight or shift any components - I actually ended up zip-tying the rx and battery to the former closest to the CG. Your Saito weighs a little less than the OS, so you may need to shift the battery into the fuel tank compartment.

Make sure you glue down your canopy. If you mount it with screws glue in some mounting blocks rather than driving screws through the balsa sheeting.

Keep an eye on your retract struts. Our field is pretty rough - lots of gravel - and I've had a couple of gear-banging landings - but haven't had any significant bending problems.