DON'T UPGRADE to v4.x.x for this, really don't please. It's not worth it. Wait for proper Atmosphere which will be 100x better.
Every since @SciresM tested HBL working on 'higher' firmwares than v3.0.0, developers have been fast-paced to do the same, first earlier this week we saw a 'hekate-ipl' mod for v5.0.x firmwares, and now here is similar mod of payload for usage on v4.x.x devices.
OFFICIAL SITE: --> https://github.com/nx-python/hekate-ipl-4x/releases
NEWS SOURCE: hekate-ipl-4.x - HBL on 4.x (via) GBATemp