Increasing a cable pattern ..... can anyone help

I’ve started a cable sweater but I’ve had to increase it by 20 stitches. It was OK doing the cable rib but I’m just about to start the main bit and realised I’ve bitten off more than I can chew. I guess the easiest thing is to add 10 stitches to the beginning and end end of each row (the pattern starts after the first 7 stitches on the 2 biggest sizes - I’ve added 20 stitches on to the biggest size as that was the increments the rest went up in if that makes sense) so each row begins and ends with,currently, a max of 7 purl on a right side and 7 knit on a wrong side.

Is my best bet just to change that to 17 and keep the rest of the pattern what it would be for the biggest size?

Here’s row 1 for biggest size …
P7, K8,p8,k2,p4,k4,p4,k2,p8 k8 p8 k4 p2 k4 p2 k4 p1 k4 p2 k4 p2 k4 p8 reptile * to * p7


Hi and welcome!
You can do that, add 10sts on each side in reverse stockinette. It’ll probably make it easier when you get to the armhole and shoulder shaping. You may have to adjust the pattern there too for the extra width.
What pattern is it that you’re making? Can you give us the pattern name or a link?

Thanks for that - what is ‘reversed’ stst - it’s not something I’ve heard before or maybe we refer to it differently in the UK?
It won’t seem to let me upload a picture of the pattern - it’s a Wendy Aran sweater pattern number 5743.

Great looking sweater!

Reverse stockinette is purl on the RS, knit on the WS which sounds like the 7sts on each end of the pattern.
I think adding on each end is easiest. You could consider adding one or two sts between cables but the cables have nice spacing as is. The central cable isn’t an easy one to modify either since it’s so complex. So, I’d go with adding 10 on each end.
You’ll be doing that on the back as well (+20sts). Is that correct? Adding a total of 40sts around the entire sweater?

Yep that’s right and yes it’s a lovely sweater. I wanted to do it in the chestnut brown on the pattern but it’s been discontinued so I’m using a deep forest Green.