Technical Merc welded rear fenders hints

Hi, about to start welding the lower rear fenders onto a 51 Merc. Before I do I would really like to hear what you need to cut out or leave under there to allow for cleaning and stability.
Does anyone add sheet under there for support or mud shield?
Do you cut any inspection holes into the inner walls?
Do you just bolt them up get them square tack and weld, or trim the tabs off the panel?
Not to keen to make a mistake here....

 

So I cant really speak about making any inspection holes ... So when I did my 49's rear fenders before thinking of welding them on you need to make sure the bodywork is 100% what your willing to work with from then on because its going to be hard to do any panel-work after the fact ie welding up trim holes or anything like that. So for doing mine seeing as my front mud shield were rusted away I remade them trying to go from the very bottom to the top and fitting with basically no gap ; and the rears I simply omitted them and made a support rod to the frame. I planned to weld the lower section onto my inner frame rails so I put in 3 "drain holes" basically just bead rolled channels that should let water out should it get in. Finally after being happy with all the metal work I primed and put undercoating on everything except about a painters tape width where the weld was going to be both body side and fender side because you'll never be able to paint once its all welded except maybe the very top most part. Once it was time to weld I just bolted everything together and slowly tacked about every foot then let everything cool then repeat till done. I left the bolts in because its filling a hole so no reason to make more work. Just take your time and I 'm sure you'll get it sorted just fine and honestly not likely you'll have a water issue unless you live up in Perth .

 

Thanks for that, sort of along what I have been thinking. I am a little concerned about getting back in there to get junk out that flings up behind the wheel ... I might just just make sure I can get a hose nozzle in and an occasional squirt of fish oil as well. In the front portion do you think it would be worth putting and inspection plate in from the rear foot well? would be very easy to do and seal and should you need to get a dolly in ther in future might help. All that said most cars dont have removeable rears quaters anyway...