The Bean Bag Helper (tm), a pretty easy DIY...
As most probably know, a bean bag has the ability to be the most stable camera support possible. Plus they can be quite cheap; the one I'm using was < $20 delivered. But that stability also inhibits flexibility, particularly when working with fast moving subjects (wildlife/etc).
There are bean bags to which a tripod head can be mounted, but I've never really understood that. It raises the CG quite high, significant reducing the stability provided by the bean bag. And in some cases the tripod head mounting point is actually quite small further reducing stability. In other cases there is a large plate for attaching a head which helps reduce the instability of the high CG... But in all cases, a bean bag with a tripod head/adaptor installed cannot be used for maximum stability/support which is where their benefit truly lies. And the cost for such a bean bag with a dedicated tripod head is really quite high for what you get benefit wise. Just the bag alone will cost as much as $130 (Apex/LensCoat).
So that got me to thinking, and I'm now prototyping a new product that I'm calling the "Bean Bag Helper." But it's also a pretty simple DIY to get something close to what it will finally be.
Basically it's a 110mm/4.5" scooter wheel with sealed bearings, to which an arca swiss clamp is attached, with a short stand off spacer between them. I'm using a custom machined spacer and screw, but you wouldn't necessarily have to. If you use a standard pan head type screw it shouldn't protrude too much or create that much additional friction/wear, and a basic washer stack would suffice for the standoff. I'm using a wheel with a machined aluminum hub, but the total weight/size is still very small/reasonable compared to a tripod head and mount.
With the Bean Bag Helper attached to the lens's tripod foot it enables easy panning and more flexibility in positioning up/down. But the low profile keeps the CG lower and the whole assembly better seated to the top of the bag compared to a tripod head.
And when you want/need the maximum stability that a bean bag can provide you simply rotate the Bean Bag Helper out of the way and snug the lens down into the bag.
The picture is obviously not of the final product... the clamp and attaching bolt/anchor will likely be notably different. But it does work very well...