Use of copper tubing?

[Charles]

	I have read in several books not to use copper tubing in a
high-pressure system with changing pressures (such as brakes) because
it will work-harden and crack.
	I'm running Teflon-lined stainless braided hose (only .42 inch OD
for #6) for all my high pressure lines.
	Does anyone have a reason that I shouldn't use copper plumbing on
the suction side of the fuel pumps? Pressure never exceeds 1.5 psi
(blowoff valve on the tank). There's a location that I need a fairly
tight 90 degree bend, and there isn't room to bend the existing rubber
hose.
	Thanks!
-Charles
'81 745i