The problem with a 2-1 (although Blair did quite well with them, also Dunstall) is what controls the primary length?
There are theories all over the place, but the bottom line is "try this, and modify as needed". Very difficult to do with 2-1, easier to make several variants and bring with.
I'm not sure if absolutely equal length primaries is necessary, especially for a peak power application, but the calculations for staggered length are really, really complicated (read Blair's work on the Ducati).
I hate to say this (because I can't weld) but that dog-leg in 1 primary is going to bite you. Not only does it reduce flow (and may introduce a "shadow" in the pressure pattern) but it will raise the temperature in that exhaust valve and seat.
Absent other design or mechanical limitations, the best primary leaves the port aligned to the flow axis (which may not be the port centerline), goes straight for as long as practical, then changes direction with a big radius.
Single pipes do not always produce the best power, but:
cheap to make
easy to modify in situ (hacksaw + extensions & clamps)
even the worst length choice is better than a badly design common system
allow megs as an afterthought (with extra support hardware)