I really don't know if these are oil cooler flaps, I just call them that. I never worked on radial piston engines, only turboprops.
Here's the real thing:
and here's what the kit came with (I accentuated the scribed panel lines:
I'd originally planned on cutting out the scribed area to install a scratchbuilt panel. As you can see, towards the front of the area it's very narrow. I wasn't completely sure if I could cut the panel away without breaking that bit or if it would even stay structurally sound. I would bet it would, but I lacked certainty. If I broke it, repair would require scratchbuilding skills that, if I'd had them, I wouldn't have broke it in the first place (makes sense?).
My solution was to make flaps and place them over the scribed area, painting the interior area black to simulate a hole. This MAY work. The problem is making the flaps look, at least a little bit, like they are rotating into the fuselage. It looks pretty good unpainted, but we'll see.
Here are the flaps:
and here they are installed. I'm sorry that the picture is after I'd pre-shaded (see below), but I mistakenly thought I'd taken good photos before I pre-shaded.
Pre-shading is a way of adding depth to a scale aircraft. I could explain it to you, but I'll let the the video by Brett Green explain it to you as he did to me.
listening to while posting: "Don't Let Go" by Weezer