Hello Safe,
PROJ.5 has just been released, and it seems to be a great improvement to PROJ.4.
It looks like all manner of "difficult" projection will be supported (with polynomials and Helmert), so is Safe planning to take advantage of this, and implement PROJ.5 support e.g. in the next major release ?
I know for a fact, that Danish legacy projections will be implemented shortly (if not already), with full accuracy, and henceforth will be maintained here. This enables centimeter accuracy in reprojections.
Cheers