Tripods are a great aid in making sharp images even though they can be awkward to use and cumbersome to transport. There are also different heads for different purposes and finding the right combination can be challenging
For those who use large telephotos a gimbal head is big plus as it helps balance the lens and greatly improve overall handling. But most gimbal heads are bulky and heavy, and they don’t work very well for general photography with shorter lenses. One popular compromise has been Wimberley’s Sidekick which attaches to a conventional ballhead so you don’t have to completely change one head for another to achieve a gimbal-like setup, or carry a second tripod with a full gimbal head attached. While this definitely saves bulk and weight, the arrangement is not as strong, rigid, or smooth to operate as a full gimbal head. Recently David and Clay Wimberley have come up with a third alternative called the Sidemount which slots between the Sidekick and Wimberley Head Version II (their current full gimbal model). By removing the full gimbal swing arm with platform and mounting the Arca-Swiss compatible quick-release clamp directly to the upper pivot point, they’ve reduced the weight by nearly a pound and improved portability. Of course your lens has to be held sideways in the clamp while you attach it, which is not as easy to do as when using a full gimbal platform, but that’s part of the compromise. In operation, the Sidemount works just like the Wimberley II with both locking knobs on the same side. In addition, the Sidemount can be converted to a Wimberley II by adding the full gimbal conversion kit. Alternatively, a Wimberley II can be converted to a Sidemount by removing the swing arm and platform and installing the Sidemount conversion kit which consists of a quick-release clamp and two hex screws, so now you can pretty much have it your way. On a personal note, I’ve used the original Wimberley head for several years and though I’ve been tempted by the newer Version II I’ve held off—partly because of familiarity and partly because I like the smoothness of the original bearing surfaces. While it’s bulky and heavy, when mated to a Gitzo GT5541LS, it pretty much removes any excuses relative to support
If reduction of weight and bulk are at the top of your priority list but you still require a gimbal head, the top choice is 4th Generation Designs’ Mongoose 3.6. This elegant machined aluminum head is a sidemount design weighing just 1.5 pounds. That it is sufficiently sturdy to do the job is attested to by the fact that Arthur Morris uses one regularly with his Canon 1D Mark IV and EF 800/5.6L lens. 4th Generation also now offers an Integrated Low Mount Arm which will convert the sidemount M-3.6 to a full gimbal head with platform, adding an additional 5 ounces.
Going in another direction, Really Right Stuff has come up with a novel twist to allow an easier change of heads on a particular tripod by offering a leveling base with integrated clamp. The idea is to permit a fast swap between ballhead, gimbal head, or video head, all with the added advantage of the ability to quickly and securely level the platform. RRS makes top-quality accessories, pretty much as good as it gets. My only concern here would be the series of connections between the camera or lens and ultimately the tripod legs. For this setup to be truly rigid, every one of these has to be absolutely tight with no give or play whatsoever, and has to stay that way. In general, reducing the number of connections as much as possible has been the mantra (hence the long-standing recommendation for 3-section legs over 4-section legs, and choosing a leg set with only a top plate and no vertical center post) in the quest for the most solid platform for your camera. But if you have (or want to use) only one tripod and really need more than one head from time to time, this looks like a convenient solution.