Yo!
I have just recently taken on the task of creating(from scratch) an " N " scale LNG Tanker Ship! it will be the twin to the regular Tank Ship(oil) for my "N'scale Module construct. As you know the older ships of this type had decks with domes where the pressure vesels for the LNG tanks were like half tennis balls above the deck! They now have Sheet-Metal tops, level on top and the sides angled down to the deck- Yet, still have the half Balls underneath!
Anway enough of the intro. Those older vessels had stairs(Shipboard-Ladders) that wound in an angled and circular tapered form up to the top of the tanks. No, I don't why! This was obvious when you looked at them! This requires P.E. Stairways.Yes! They had handrails on both sides And a little Square area, Or Round Area , on the exposed tanktop.
Nowadays, There's just a walkway the length of the deck where the housings are with a normal ladder up/down at one or both ends! These older ships are the ones we will be talking about! Take the Longest ladders (stairs) that you have been able to get in 1/200. I am not sure if you can even fine some long enough in 1/87! Now at the proper angle, Oh! they must be fully formed as Stairs/Ladders and fastened at the bottom all the way across the tread width!! Now slowly form them around the ever smaller tank top. Once formed to the top, C/A glue them in lace up there. One spot of glue every four steps will ensure they keep their shape!
Create the little porch on top and put the rails around it. I believe there are some valves up there, I will admit I am not sure! just make it look a wee busy on the Porch floor! Paint them the same color on top and underneath and the rails in the tank color( Usually White) then paint Yellow edges or Treads on the steps(Safety First) Must be the rule
In case you can't find them in the H.O. Scale 1/100 will work! Just be careful , Oh, you Cannot wrap them around a tube and then form them out. Try that and you will destroy the P.E. If you have any questions on some of this odd P.E. useage just message me, I am here for you! WARNING! WARNING! This is for Oddball Ship and Whatever Builders only who like to tear up the norm!