Seat harness cut outs

[Dave Ed 52]

Has anyone fitted their own harness grommets to their seats. 
ive just fitted some Westfield seats to my Exmo but as the harness now passes around the sides of the seat, my co-pilot (8) isn’t as well secured as the harness now slips off of her shoulders. 
I’ve seen some online but it means cutting into the seat. Does anyone have any pictures or experience doing this modification? 

[MarkBzero 296]

Hi Dave,

When my son was younger I used one of these and worked well.

https://www.ebay.co.uk/itm/323979320399

[Dave Ed 52]

Ah, that looks perfect. I was looking for something like this but couldn’t get any of my search descriptions to display them. That’s a lot cheaper than the seat grommets I was looking at. 
My only concern is how the straps come over her shoulders first. I’ll have to do some trial fitting with my little helper tomorrow after work. 
thank you. 
 

Edited May 25 by Dave Ed