If you have the time/interest to try a few experiments, you might take a look at this option:

Basically make the headers in 3 main sections (1 2 3 in the picture) you can weld up the primary collectors to the secondary pipes, but don't weld them to the primary pipes for now. Same goes for the final collector - leave it out (but construct the secondary pipes so that they will fit the collector.

Then you could get short lengths of pipe - a couple of inches long, and expanded at one end (so they slip over) - which are like mini extensions to vary primary or secondary pipe length and do some testing. You could start with no extensions at all like in 5, or otherwise could add to the primary length a couple of inches, or the secondaries (or even both) as in 6. This is basically making them like lego - and you can alter the lengths to find the best powerband. You could probably even (for racers) run longer primaries or secondaries on tighter racetracks, and shorter ones for high speed/long racetracks. You could keep them modular like that and adjust them as needed, instead of having to have 2 complete sets of extractors/headers for different tracks.

Naturally you'd have to also check whether they will all fit into the engine bay without hitting something, I just presented the idea because I just got back from work and can't get to sleep!