LOL one more thing you could try if you havent already, sounds like you have already tried everything but you can take a grinder and bevel the edge of the truss piece and turn your amperage down a bit, you should get plenty of penitration but without needing as much heat..... Anyways good luck, Im goin to keep an eye you do some good work and have some perty lookin welds...
![Beer Chug\'n :beerchug:](https://board.marlincrawler.com/Smileys/marlin/beerchug.gif)