Flow rate through lobster back bends vs mandrel

Hi all

Any thoughts or comments on the use of lobster back bends when forming an exhaust manifold.

I am making one for my Skoda using some 35 mm exhaust tube. It will have a 4-1 manifold with some fairly long primaries. I am home-brewing the whole lot and I would obviously prefer to mandrel bend the pipe, but I have no access to a suitable bender. I have ruled out the use of pre-bent tube due to cost.

I have found and installed a program that outputs specifications and templates for cutting lobster back bends. Any thoughts on their use with exhaust primaries?

I had planned to use a good number of sections i.e. 5+ for a 90 degree bend, and then die-grind the inside of the bend to help smooth it out. Will it be good enough? I imagine lobster back bends would be better than pressed bends due to maximisation of the cross section of the tube.

Thanks

Lewis