Karl and Ian never intended for the WWSD rifle to use back up iron sights, so the handguard was not designed for this purpose. Standard height MLOK rails will be too tall when mounted to the carbon fiber handguard, making the point of impact too low to be able to zero.
The only way to successfully mount iron sights we are aware of is by using the Arisaka Defense low rail
We have tried this with MBUS sights ourselves and it does work. Be advised though that all free float tubes, including the carbon fiber ones we make can have zero shift depending on how you load weight on to them. Iron Sights should be a back up sighting system in the event of optics failure, and should not be used as a primary sighting system with the WWSD.