I've seen that PatchMyPC has recently added SecureFX to the catalog. However, i would suggest adding the "SecureCRT + SecureFX bundle" as well, as there is a difference in the two installations. The standalone SecureFX doesn't know detect the older version of the bundled SecureFX install. From what i've tested myself, if you install the standalone version of SecureFX, the installation path would be "C:\Program Files\VanDyke Software\SecureFX\". But if you install the bundled version, where both SecureCRT and SecureFX are bundled in one installer, the path is "C:\Program Files\VanDyke Software\SecureCRT\".
Hence, due to this I noticed even after adding SecureFX to my catalog, it wouldn't detect and update my clients, as they used the bundled version. However, when I removed and put in the standalone versions of CRT and FX, they both got updated with their individual patches.