Mk2.5 O/S/F chassis rail repair

Hi I have a mk2.5 and the o/s/f chassis rail has rust on the outer side I am wondering if I can weld the new rail repair panel on the outer side and underneath along the bottom inside with having to remove the radiator. The inside/ engine side has no signs of rust it’s seems that its starting to slightly go on the outer side where the anti roll bar bracket is.