The baffles cannot work all by themselves. They need to make contact with the cowl around them. Foam, cardboard, anything that will close the gaps. In the picture below I made a cardboard system with baffle and short jacket inside a round cowl, which can be seen through the somewhat transparent cowl.

In front of the baffling system the cylinders are cooled by the air turbulation of the prop. Behind the baffling system the hot air is drawn out through the slit between cowl and fuselage, which probably is quite efective. Louvres like in a suchoi will provide excellent air extraction as well.