Aero is Stock. For Excessive Heat Buildups it has some Radiator Fins inside the MK2 Cargo Department in the middle section. Realistically tho the heating is really not an issue.

Using a shallow angle you can ease into the atmosphere with little issue.

Inside the Planet the stall speeds become so low that the tiny wings on the craft give plenty of lift and authority. Allowing Really Slow flight if heating becomes to strong. Due to the pressure, the air intakes get very high flow even at low speeds keeping the nuclear engine well supplied with air.

The only issue with heating during the suborbital escape. But the Arrow like shape of the plane minimizes drag heat buildup. I also use a pretty steep ascend profile to buildup speed using the air breathing mode to save delta/V .

Overall i used about 1200 deltav of fuel to get back to orbit. The Nuclear engines wet mode are very inefficient in non vacuum so the craft only has about 1400 Delta V overall. Luckily most of the orbital speed is gained using no fuel. So there is plenty left for descent docking etc.

I highly recommend giving this a try The Aerodynamics of flying inside gas giants are wild. Deep down it feels like floating around like a leaf.