try a top-stitch or universal needle in the appropriate size for your thread- probably a good 40 wt will work just fine. as for tension- you will probably have the best luck if you use the same thread in the top & bobbin- and just stitch a 'test' piece and adjust until your tension is equal- i've made lots of things using timtex (the heavy weight interfacing used for baseball hat brims) and have not had a problem --- i never use a walking foot though- i just use my regular 1/4" foot- you may need to slow down a bit too-