100% on the baffling. And another 2 points from my experience. Make sure the fuselage interior is well ventilated; both the -90 and -60 carb trumpets protrude behind the firewall and feed off the air plenum of the fuselage interior. The speed variance of the plane can create varying pressure differences inside the fuselage. Furthermore, higher "ambient" temperatures can bleed in from the hot cowl compartment, also affecting the breathing of the engine. Both of those may start spoiling the tune of the engine halfway through the flight, resulting in gradual power loss and "laboring" operation. A small inlet on one side and some venting holes in the back neutralise both dynamic effects. Just my 0.02.