Knitting Fair Isle (or other stranded colourwork) from the bottom up

I prefer to knit items in such a way that they can be constantly tried on to check for the perfect fit, however most stranded knits are done from the bottom up, in 3 pieces which are then joined at the yoke and then knitted as one piece. As my husband is tall with a slim/fit build it is difficult to size things for him perfectly and as I've had to cut, then pick up and knit an item longer I really wanted to avoid this happening again!

First I looked into increasing with fair isle knitting, after a lot of searching I was able to conclude that when increasing there is more room for error when it comes perfect symmetry, however when decreasing the decreases fall evenly in the middle and are very pretty. If you were knitting something with rest rows or a pattern that didn't require symmetry this would not be an issue, but for an item with peaks or little triangular shapes it makes a big difference. So this idea was out!

I ended up doing a provisional cast on for the required number of stitches at the yoke (after sleeves where attached). I then knitted this from the bottom up, after completely the yoke I had the intended owner try it on to see how far I should knit down. 

The provisional cast on can be seen here in the blue cotton, after trying this on I also realised I am not completely happy with the collar. I will likely rip this back about 1 cm as I think it will sit nicer. 

I was able to see that the cotton sat about 2cms above the area that the sleeves and body would normally be joined, so I knitted down to here and tried it on again. 

Once you're happy, look at the pattern again and see how many stitches are needed for sleeves, body and underarms then divide up your sweater with stitch markers. We now treat this sweater like a top down circular or raglan sweater. 

fair isle sweater in Lopi

Place sweater sleeves onto waste yarn.
 
Knit across work to sweater, then either cast on require stitches for arm pit or (my preference) pop another provisional cast on here for the required stitches. This then leaves stitches live to be picked up and creates a completely seamless sweater which is very tidy.

Body is now knitted down in pattern, making adjustments as you go, once you have finished its time to start with sleeves.

Pick up stitches and knit sleeves down in pattern! 

And that is how you have the best of both worlds