Hey David, this is actually a great question. In designing my last project (kitchen island) I ran into a lot of questions related to casework/carcass design and the answers can be difficult to find. It looks like you have a pretty solid design based on your model. Generally, here’s what I’ve found is required in order to make a drawer function well:

Drawer runners: support on either side of the drawer that the drawer will slide on top of
Drawer glides: Lateral supports on either side of the drawer which resist the tendency for the drawer to rack within the case
Kickers: Support above the drawer which prevents the drawer from tipping forward as it is pulled out

There are a ton of different ways to incorporate these elements, but it looks like your design has all of them. As far as I can tell, the drawer runners for the drawer above will serve as the kickers for the drawers below and these horizontal runners/kickers with be incorporated into vertical glides attached directly to the panel.

Two recommendations: there should be a separate kicker above the top drawer (which might be incorporated into the top not shown), and I would recommend doing an M&T joint for the drawer glides into the legs for added strength. The drawer runners can then be screwed into the glide and the structure will be very strong.

Hope this helps,
Andrew