I meant sticking a standard plastic airline style carrier in underneath for the second boy, so they’re separated and can’t punch on.

But I think even if modified for more room the dimensions of metal frame wouldn’t allow that

Edit. This is what I mean. The smaller fabric shelf and front Pawz panel could be removed and replaced with a larger shelf, if it was large and rectangular enough to hold a standard plastic carrier. Like these for under rollators or wheelchairs.

But the room below might not be enough and could cause issues if the bottom carrier was riding too low.

And the width of the plastic carrier might be too much to slip between the pram legs for that little extra room for the top front edge.