Just because this is fun, I’ll note that the gravity near the surface of the cylinder and near the middle would be unusual; it would drop off as 1/r instead of 1/r2 (since the cylinder isn’t of infinite length, at some point this effect would fade and the usual 1/r2 dropoff would return - but still interesting).
This sounds like a really bulky method of making a tractor beam.
Ok, so we are all disappointed that we don’t get a massive gravity pull at the end.
But I still think we can get some over the top forces if we do a new experiment. Suppose I sliced the cylinder at the mid point, slipped a penny in between the two halves and then let them come back together. How much pressure would such a penny be under, having the equivalent of a 3 billion mile high mountain on either side of it. Would it be enough to force atoms of the penny into an interesting form of matter? (e.g. neutron or dwarf star?).