I'm making a tarp out of 2.2 oz/yd coated taffeta (got it cheap) and I'm having trouble sewing the four layers needed to sew a felled seam. I'm using a 90 guage needle and it skips stiches badly and seems to "bounce" off the fabric.

What size needle works most effectively for multiple layers of 2.2 coated material? Will I need an even larger needle to attach webbing tie-outs?

I'm thinking of going to a general -use / 100 guage needle for the felled seams and maybe a 110 to attach the nylon webbing tie-out. I tried a much heavier needle made for sewing bluejean material and this jus bounced around also.

Any help from experienced DIY'ers will be most appreciated.