While designed for the specific purpose of fitting into an X-MAXX, the DS1885BLDP is quite an impressive specimen as servos go (ditto the -M variant for fitting to an XRT). Outfitting either with beam-mounts (like those of DS1505, DS1735, DS2180, and DS2685), gives you the added benefit of versatility because then you can repurpose this specialized form factor for another application.
Included are two bolt-on beam mounts, which CNC-machined from a solid billet of 6061-T6 aircraft aluminum. Also included are four machine-thread Allen-head mounting bolts for attaching to servo.
ProTip: install mounting bolts with thread locker. When/if the time comes to remove them, first use heat from the tip of soldering iron (setting it point down inside the pocket of Allen head socket to soften for maybe 5-minutes). Do this, before trying to remove them and the thread locker will release relatively easily.