What materials were you planning on using-- what qualifies as "too heavy" for you? Are we talking you need a pit that weighs less than 50lbs total, or 100, or 200? How are you quantifying the time it will take you to set up the pits? Do you have any CAD files of the rejected pit designs? Do you have any budget constraints for the project? Is the goal to get this assembled for use at a 2014 regional?
As a general rule, it's a significantly more useful experience to get feedback on something than to have it handed to you.
I would recommend looking at this paper from 1334 for ideas.
Also, unfortunately, I can't exactly provide you with specs for my team's pit, as
it isn't exactly homemade, persay...