More hydraulic questions-Long

The Honda tractor I want to add hydraulic cyliders to has two
single acting cylinders. The manual says to not keep the valve handle
in the raised position after the implement is at position. This is
because the pump can be damaged. The handle has a spring return so
letting go unloads the pump.
My first thought was to just put a power steering pump on the front
PTO to power my added cylinders.
Looking at the pump in the tractor today I see that it is a gear
pump. Since these are positrive displacement pumps there must be some
sort of bypass that keeps things from breaking when the cylinder
reaches end of travel. This, I think, is why keeping the pump
pressuring a cylinder can cause damage. The bypass just bypasses
internally and things can get hot fast.
But when the pump is filling a cylider the oil is not bypassing and
heating up. I think that if the pump was pumping into the reservoir it
could do so for long periods of time without the oil getting too hot.
Looking at the way the cylinders are actuated, where the valve is
located, makes me think that this is what is happening. The pump is
spinning all the time as near as I can tell and it is just
recirculating the hydraulic oil.
This makes me think that if I plumb the front cylinder oil port
from the tractor's hydraulic valve into an open center valve I can
use it to power my added hydraulic cylinders. I would need to somehow
lock the tractor's valve handle in the on position and then use my
added valve to control the added cylinders. Does this make sense?
BTW, reading online about hydraulic valves I ran into some
definition problems. Open center valves were described, in several
references, as valves that when centered would have all the ports on
the valve connected together and open to the reservoir return line.
This means that this type of valve would not hold a cylinder in
position when centered. Then, reading further I see that the kind of
valve that holds the cylinder in place is called a Tandem Center
valve. I think. But that they are commonly called Open Center valves
in catalogs when the valve is manually controlled by a lever of some
sort, instead of by a solenoid or similar. And typically used on
mobile equipment. Is this correct? I can just order an open center
valve with levers and expect it to hold the cylinders in place while
at the same time returning oil from the pump to the reservoir?
Thank for reading,
Eric
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etpm
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