would people recommend cutting the cloth so that there is no overlay on the glass join, or hasving an overlap and doing a bit of sanding?
Gillard, you need the overlap left in place when you finish with the build phase of your project.
And the following info is not directed at you, it is just a top-level review of basic structural engineering principles (and not even limited to "aerospace" structures), it is more like a warning to those who apply one layer of glass and then sand off the overlap
While I am not a high-power flier, or builder, I can tell you that without a region of overlap along the seam, your completed tube will be little stronger than the underlying material. You will need an overlap that will probably be at least 1/2 inch to 1 inch wide (overlap width depends on the inter-laminer shear strength and the design margin you wish to use). Depending on your building skills, the overlap may need to be wider to end up with a good, usable overlap zone.
If the two sides of fiberglass wrap material are brought together in a butt joint, you will have a weak "spot" (actually, a line) that extends the length of the joint. The only structural strength your tube will have is whatever properties the underlying material has. If you want the fiberglass to do any good (other than adding weight) it has to be a structurally complete layer, which requires either:
--reinforcing material woven in a continuous tube or sleeve shape that can be pulled over the length of the underlying body tube; the sleeve fibers must be continuously woven around the complete circumference with no joint or loose ends (I think woven carbon-fiber reinforcement is available in "sock" form but I don't know about fiberglass---seems like it should be?)
--reinforcing material woven in sheet form, cut to fit the underlying tube, and rolled into place with a sufficient zone of overlap
which must be left in place; if you subsequently sand off and remove the overlap, you are effectively right back to a butt joint (at least, structurally speaking)
If you want to smooth the exterior as much as possible and reduce the visible exterior ridge that forms at the overlap, your choices are:
--change to tooling that lets you control the OUTER contour, that is, mold your fiberglass tube on the inside of a smooth tube-tool surface with pressure applied from the interior (balloon? bladder?) to push the fiberglass material against the mold surface; for almost all of us, this approach is way beyond our construction experience
--use conventional fiberglass wrap techniques and apply an outer layer of peel-off surface smoothing material, bleeder cloth to absorb extra epoxy, and an outer seal wrap, then apply vacuum to the whole thing to suck down the surface smoothing layer; this will reduce the amount of "bumpage" but will not eliminate it completely
--use conventional fiberglass wrap techniques and follow with a layer of microballoons (in matching epoxy); sand the microballoons
Again, if you sand off the fiberglass overlap, you have weakened or eliminated the structural overlap. And if you're going to do that, then you might as well skip the fiberglassing entirely.