Yes those fish are pointy but they are not in asealed environment ! If the piston is releaved of work (suction as you call it) by the taper . The benefits will then be cancelled out proportionally by the pack above and vice versa.
Yes you can compress a fluid by a very tiny amount with about 100 tons not really applicable to our toy cars.
So therefore taper up or down it makes no difference as does the taper it's self
Please don't shoot me down. Just trying to be helpful
Valves are the way to go
On a dex
Drill a 2pm hole in a piston and keep your normal holes also then screw on top with the piston securing screw a thin piece of polythene wide enough to cover the 2mm hole but not covering the normal holes.
Hope this makes sense as I am typing and roofing at the same time lol
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