Hi, Beverly!
Actually, this should be quite easy. All you have to do is adjust the gauge. For instance, say there are 140 sts across the back of the sweater. If your gauge is 7sts/1", then the back will be 20" wide. So, since you want it wider, why not use a yarn and needles that will give you 6sts/1", which will result in a back that is about 23" wide and a finished chest of 46" (this is only an example, you can adjust it to get the size you want). Although I haven't been able to start swatching yet, this is how I plan to size up my cardigan.
Hope this helps - Maria

I also need to upsize, and am going to knit the sweater at a larger gauge. For one thing, I tried a swatch in a bulky yarn as recommended, with 4.5mm needles, and found that knitting at that tight a gauge was just too hard on my fingers. I am now going to try using that heavy yarn with a more normal needle size.

I will probably still have to add some stitches, but may repeat a cable instead of filler stitches. If I do add filler stitches, it will be under the arms -- I think the appeal of this sweater is at least partly based on the fact that there is very little filler between the panels. That, with the tight gauge, gives it the dense look that makes it unique.

Ann

I will need to upsize my cardigan too and plan on trying to come out with fewer stitches per inch than the 7 called for. I'm aiming for 6.25-6.5 per inch--need to take some good measurements to refine that number a bit. My yarns for swatching just arrived yesterday. I had tried Briggs and Little Regal--good for width, but way short on row gauge. Cascade 220--much too loose with an 8 and gauge too off with 7 US. I have two skeins to try--well, three actually--to knit and attempt to get gauge. I have two that are very close to the yarn called for in the pattern in terms of yardage per 50 gm ball, so I'll try those 1st. Wish me luck!