My first question is ... is a jumper a sweater?
26 for the sleeve length sounds a little short to me if he is over 6'. My hubby is 6'5" and he wears a 37 sleeve and is a 44 chest, neck to back length on sweaters is about 27-29". Hubby just came in from deck building so not likely to let me measure him, but he is well over 14" wide across the shoulders....I'm 5'11" and my shoulders are more that 14" so I would check that again maybe.
Men do like sweaters to be roomier than most women (we like to show off our figures) so if you know what size her wears maybe go measure a sweater at a local department store and see what the measurements on that look like.
Best of Luck to you knitting your man a sweater. Mine gets socks, scarves and hats - period. I don't even try to buy his clothes let alone make them :teehee: