SplatMesh 
PacletDirectoryLoad[NotebookDirectory[]];
<<CoffeeLiqueur`Workshop`SplatMesh`
Filtering Gaussian Splats
mesh = Import[FileNameJoin[{"attachments", "Untitled scan-663.spz 2"}], "SPZ"]
Graphics3D[Scale[{mesh, Cylinder[{{0.0053`,-0.0088`,0.0077`},{0.0017`,0.0902`,0.0119`}}, 0.7/30.0]}, 100], "OrthographicCameraZoom"->5]

{x,y,z}f = RegionMember[Cylinder[{{0.0053`,-0.0088`,0.0077`},{0.0017`,0.0902`,0.0119`}}, 0.7/30.0]]
[index, center, scales, quaternions, opacity, color]
filtered = SplatMeshFilter[mesh, (f[#2])&];
Graphics3D[filtered, "OrthographicCameraZoom"->26]
filtered["Preview"]
Export["filtered.spz", filtered, "SPZ"]