Heavy duty sills/cills

My first question guys. Although the sills on my 300tdi are relatively sound and may require only a few patches. Now i have a lot of the dody panels stripped off anyhow I would prefer to replace the lot and I am interested in fitting the heavy duty 3mm box section that appears to be popular, My concern is the legalities with insurance companies, has anyone had major problems once they have been informed that they have modified the sills??
Cheers

I done mine out of box.didnt bother informing the insurance

Same here - I view it as a repair

As said,its a repair not a modification.

same here,

I used 4 by 2 box galvanised from a local steel supplier

cost buttons, MOT man thought it was a great job, i suppose if you put jack points into for a side jack, it could be a mod, but to me , its a repair