Over-sized FOD screen should give adequate protection if it enclosed the engine front. We don't recommend a silicone sealant as this can come loose overtime and will be sucked into the engine. On my engine, I don't seal the back of the FOD screen against the engine cover. I use FOD screen that is about 1-2 cm larger than the engine diameter and just let it sits centered over the starter. When the turbine is running, the suction will pull the screen tight against the engine cover.

Keep it simple and make sure that the mesh is not too fine. Remember that if you reduce the intake air volume, you will raise the EGT and decrease the thrust output.