Hi Bigfella,
If you fit a copper pipe, you may as well just use it as the manifold and forget the s/steel braid.
The only advantage with the pipe inside and the slots facing downward would be that you would drain a tad more wort from the tun as the syphon would continue until the level reached the slots.
Of course, this could be a litre or so in a large diameter tun and the larger diameter the braid, then the more you leave behind.
As Batz said, use a "T" and join it, or if you are worried about the wort left in the tun and you are considering copper, then check the designs of manifolds in JJ Palmers book - "How to Brew"
The amount that is left behind can always be compensated in your Promash / Beersmith / similar, software, by adding a bit more grain to the mash.
Cheers