How to pay more CMS?

[Heisenberg17]

So I am writing this on behalf of my husband. He has a son from a previous relationship and has always payed child maintenance. The arrangement is between him and his ex and he pays a set amount for him each week. With every day living costs rising my husband is keen to increase his child maintenance.
Him and his ex have a very strained relationship so he’s not sure how to approach this matter as he doesn’t want to offend her in thinking she can’t provide for him, he just wants to contribute as much as he can.
So how would you approach this?

Could he maybe say inflation is due to hit 8% this year so he will increase his contributions by the same amount?

Or do you think he wants to increase it higher?

If it would cause offence could he pay more for clothes/activities/allowance so that she is paying out less from the cms maybe?

Could he say he's had a slight pay increase so he's adjusted the payment amount accordingly?