Bumper Rules on a U Bot Chassis

[ICE_Bear]

We were going to have an open front for our robot that's short enough to go under the low bar... We will have about 4.5 inches on each side of the front of our robot that's actually our frame. So we will have nowhere to connect the bumpers on the front. And since our chassis IS our frame since there is no other metal or anything other than electrical wiring above the chassis. What do we do? We have no mentors to help us interpret the rules and help us change our design if we need to.
So basically right now, we have all of the electrical and mechanical stuff set up very basically. We just have a chassis, so with the wheels, the top is at about 5" from the ground. We weren't planning on having a front part of the chassis so that we'd be able to have an attachment to help open the portcullis. So now I'm kinda stuck now trying to understand the bumper rules and see if we can still use our design at all.