I have two fillports in the top of my case, one of which is connected to nothing and is a monumnt to folly,
Do not plan on putting any bends in the fill tube or you will wait until your great grandchildren are old before you get the fluid in - and the system burped.
Instead, plan the precise location of the reservoir first and then place the fill port precisely above it so the tubing is straight in even though it be eccentric to the case edges.
My second fill port is just so and works a charm.
As to using tie-wraps?
I think you would be no better off than with the nylon ratchet clamps. The problem is that they "give" in time and that one ratchet point may be too lose while the next one may be too tight.
Oetiker clamps are gloriously good, but worm clamps are almost as good.
I used a combination of the two. Where I was sure I'd not want to open the loop, I used the Oetikers. Where I thought that one day I may open the loop, I used Ideal worm-gear clamps.
You may buy the Oetikers in bags of 25 for about $7 from McMaster-Carr.
Go here:
http://www.mcmaster.com/
. . . and search for Oetiker.
Puchase a Channel-Lock front-jaw cutter/crimper from Sears.
Have fun,
Joe