You could add one more pattern repeat (6 stitches) to make it a larger size or you could go up to size 6 needles and follow the directions.
If you choose to do the extra pattern repeat just remember to add on those extra stitches to your final stitch counts
for example on the back for instance, in the pattern it ends with 49 stitches, Just follow the shaping as the pattern states and you will have 55 stitches to place on the holder instead. Make it longer by adding more row repeats on the lacy parts for the sleeves and the body.
At first I thought it was done top down in the round but it's a four part pattern, easier to alter the four part.