adjusting pattern to fit larger size
I have just finished 'fisherman rib' jumpers (sweaters)for two of my grandsons, using an old Patons & Baldwins pattern. Their father (my son) has now asked me to make one for him to match! Unfortunately, the pattern only goes up to chest size 30" and he is chest 42". Although I am quite a good knitter, I have no idea at all on how I go about changing a pattern to fit a larger size person. I've look for a similar pattern for an adult, which I could perhaps adjust to match the boys, but no luck. Obviously this will be quite a labour of love, making something to fit my son, and I don't really want to attempt it without some idea on how to do this size change.
Has anybody got any ideas please?