the inlet ports on crossflow head point outwards so if a manifold from tubs is mead, the tubes angling in at the TB duie to their fixed spacing, there will be an angle from manifold to cylinder head - do people worry about that?

Secondly TBs I have, from ZXR6, at inlet side have a machine oval port and a cut aout above - again fitting onto a tube tuype manifold means there will be a change of area - again is that something to be concerned about.

The ideal manifold would need to curve the air in to the cylinder head port and I guess match the shape of the TB.

Lasdt one - can manifold be made from glass fibre? Can you get High Temp/ fire/petrol resistant resin? Or any other to DIY moulding from high temp plastic?

Or two slabs of ali split down the centre horizontally (wih gasked in between) in order to machine ports to the ideal shape?

If I was putting TB's on an Xflow I think I would look at adapting a DCOE manifold. They are quite common second hand and cheap as well (compared to other engines).

I made a steel manifold and spaced the throttle bodys out to suit.I used gpz1100 throttle bodys which are 35mm bore and easily mated to 38mm tubing using rubber hoses.
I would think trying to make one from grp would be far more difficult although there must be a suitable resin available as I have seen petrol tanks made from grp in the past.
There are some pics in my archive and they will soon be up for sale along with the engine as i am now fitting a zetec.
Paul.

Paul , you have u2u