For the testing, we set up outside on the black top. This way the blocks wouldn't have far to fall and wouldn't dent flooring or tables. We used two blocks on each side to raise the structure off of the ground, and each side sitting one half inch on the block. I added the weight in one pound increments. We kept going until we reached 100lbs or the bridge crumbled. Surprisingly, many bridges made it to the 100+ club. Most kids then wanted to try standing on their bridges to see if it would hold them. We found that typically if the bridge held 100 lbs, it also held 150 lbs. I stopped them when they started trying to hold each other and stand on their bridges. :) The strongest bridges were the ones with the shortest distance between the bases and the most popsicles stacked on top of each other for reinforcements. Although the longer bridges looked better, they didn't hold up nearly as well. We are halfway through testing the bridges and its been a fun, engaging challenge!