As I’ve said before I’ve seen some rusty cars in my time as an mot tester , I’ve seen filler, chicken wire, paper, fibreglass and even concrete in outs sills 😮😮
Any rust prevention is better than nothing , an old fitter I knew would spray old engine oil under his cars, would do it yearly and worked well .
With the SC430 the floors/suspension can have anything from light rusting to corrosion that needs to be knocked off with a hammer !
I’ve see cars professionally undersealed were I would use the phrase "you can’t polish a turd"…the garage took the money but the car was well past its best.
….it just masks the corrosion to the mot tester and the next person that buys the car .
Below are two examples of light rusting and holed suspension mounting point on the SC430’s rear suspension.
Depending on your ability any rust prevention you can do at home is worth it ,for me FERTAN rust converter then DINITROL 4914 underseal spray works well, and can be topped up yearly as required .
waxoil is wonderful stuff but you tend to get more on yourself than the car !
hammerite paint is also better than nothing but tricky to apply with a brush.
Any rust you can prevent has to be good for your pride and joy 👍🏻