When selecting a head, one wants to pair the legs with a head that will not compromise the stiffness of the system as a whole. On the other hand, a head that is too big adds diminishing performance increases and just adds weight.
Below is the optimization result for selecting a ball head. This chart plots the stiffness to weight ratio for this tripod and each ball head that I have tested in blue dots versus the stiffness of those heads. The red line is a generalized model for a strong performing ball head. The higher up on the this graph the higher stiffness/weight performance of the system. More information on this analysis can be found in the ball head choice optimization page.
This chart is telling us that we want to use the biggest beefiest ball heads available to pair with this tripod. In fact, this chart even understates how stiff of a head we want. The chart is generated from the stiffness of the tripod at full height. At more typical shooting heights, the tripod will be stiffer which would imply an even stiffer ball head is optimal. The point is a moot one though, as we already want to be using the largest heads available regardless. The CP38-L4 is a heavy enough tripod that there is little downside from a stiffness/weight perspective to using a heavier head. Plus, you get all the ergonomic and smoothness benefits of a larger ball.
Don’t make the mistake here of pairing these legs with a smaller lightweight head such as the Acratech GP. If you insist on going down this route, you may as well use a lighter more portable set of legs as well. The large size of the CP38-L4 makes a great platform for the larger geared and pan tilt heads. These heads tend to be much less stiff than ball heads, so again, don’t skimp here. Get the most stable ones available.
Note that these recommendations are limited to the tripod heads I have tested. The more general discussion above should provide adequate guidance if your head of choice is not listed.
FLM CB-58 FTR – This is the largest of FLM heads and pairs beautifully with these legs. The head performs beautifully and is packed full of useful features not found on any other head. Plus, you get the clean look of staying within FLM’s design language.
RRS BH-55 – The BH-55 is a classic and for good reason. It has excellent stiffness, ergonomics, and build quality with the benefits of a low profile head. It is heavy, but that is less of a downside when paired with a heavy tripod like this one.
Sirui K-40X – Easily the best value head on this list. The performance is excellent. It only falls a little bit short of the rivals on this list in terms of ergonomics and build quality.
Markins Q20i – Included here because it is technically the highest performing head on this list based on the graph above. The Q20i is really more of a midsize head though and doesn’t have the base diameter to fully take advantage of the large cork top pad on the FLM CP38 legs.