1/8 = 2/16, thus 3/16 should be 50% heavier. Steel doesn’t change density as it scales. So, if your frame is 52 lbs more, than at 1/8 it must have only been 104 lbs. I only ask because that sounds light, although it isn’t very big, and in reality you are probably talking about 0.120 and 0.188 wall tube. In the end, it is highly unlikely to matter, either in weld quality or ability to tow. The extra time to rust through and better threading of blind holes is probably a bigger advantage to going thicker, but 0.188 seems really thick to me.