An alternate solution is to add a long rail and clamp. This would have the same benefit as a collared lens foot in that it would allow you to balance the lens on the ball head. With this configuration your Q3 would perform very well.
Kirk makes a simple long rail, and Markins makes something similar with added support for the lens nose. I believe RRS also makes something similar to the Kirk long rail and clamp. Just be sure the clamp is oriented properly for this configuration.
Even if you upgrade to an M20 your 18-300 will probably still be more difficult to manage in a sweet spot than most lighter lenses and/or lenses that are shorter and don't extend as much, or collared long lenses. I've never handled the 18-300 but I suspect the heavy front element is quite a bit forward at 300mm, where precision is most needed.
In other words, this is an interesting and helpful solution for any ball head and your lens.