Wheel pants that do not enclose the brake assembly are basically worthless. In the case of Pipers they were less than 2 knots over bare. The post-78 pants were a 7 knot increase over bare, as they are fully enclosing and faired the strut as well. I empirically verified this when I owned my 83' Warrior II.
The biggest penalty on a per capita basis is not the mains, it's the nose wheel. This is because it sits in the thrust slipstream, and the effective freestream is higher and turbulent, and the drag goes to hell in a handbasket. You also have to streamline the strut, which is a huge drag component. This is not easy to do and retain serviceability of the strut (aka even bigger PITA than just checking tire pressure on mains).
This is why airplanes like the Mako are such a thing in the first place. They realized the mains can be streamlined well enough not to matter (see all modern pressure recovery setups, Cirrus, RV et al), but the nosewheel had the added difficulty of the accelerated turbulent stream, which does benefit greatly from outright retraction.
