winter protection

Hi.
I am thinking of ways to look after my chassis through the winter. At the mo there is underseal under there but its very old. Should I clean the old stuff off or leave it on there? Should I wax oil inside the chassis? Does it matter I cant clean it all out before hand?
Is there any holes anyone recomends to add in the chassis for drainage or anything?

Underseal should be ok, can always paiont over it with more underseal if wearing thin in places.
I would recommend waxoling the chassis and no you dont have to clean out whats already there. Keeping it probably helps protect it tbh.

The current drain holes should be okay. When I stripped mine down the only mod to the chassis I did was to weld a plate over the lip of the rear crossmember to get rid of the water trap there (i.e water runs down the plate instead of pooling by the x member

I like to pressure wash everything, does involve getting wet to do it properly then have a good poke about to find areas that need attention.

Any rust patches, loose/flakey paint I clean up re-paint then under seal the whole chassis. Then wax oil the inside. I also squirt wax oil above the rear floor supports, up inside the door pillars on the bulkhead. If your really keen you can drill small holes in the steel frame round the doors and squirt some in there too

Pressure washed and wax oiled my chassis a few weeks ago after Nitmare welded new dumb irons on to it. Even took door hinge screw out to blow wax oil into bulkhead. All looks good now. I use a paraffin gun to apply the wax oil. MOT man was well,impressed!

Fantastic thanks for the advice. I cant see drain holes for the tow bar boxing part of the chassis. Is that ok to leave? I jet washed mine and the amount of mud came from under it. Theres still alot there but its so much better!