you can use pushfit tap connectors. it does not matter if the connectors poke through, just use pipeclips as normal to hold all pipework in place.
Does the fitting not have a male threaded end on it? just use a tap connector it is the easiest solution mate.
enough pipe to run through the other side of what ?put the tap connector on first then fix the shower to the wall, have enough pipe to run through to the other side to fix the rest, simple.
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