Most of the Metcalfe kits are for Midland and the S&C. The coal stage is loosely based on the MR standard design; the shed is based loosely on Hellifield's straight shed. Looking at photographs however there are obvious differences, and Hellifield's 4 road shed has been reduced to two roads and about half its length. The Midland tended to go for roundhouses (see Barrow Hill), but had quite a few straights as well. Hellifield had standardish coal stage but was unusual in that it was wood rather than brick (and in later years it fell apart somewhat). The Metcalfe kit represents the more standard brick. The ramp at Barrow Hill survives (although the coal stage fell down/was demolished) - the whole thing is 530 feet or just over 2 metres in 4mm scale from the point, add on a 100ft headshunt and it's 2.5 metres or so. ouch.
When you're having to compress everything else though, especially in OO, trying to recreate the ramp into the stage is a nightmare. The ramp ends up dominating the planning, especially if you want to put it where it should go, which is just outside the shed, on its own loop (to allow access to the shed when there's engines being coaled). And of course you can't have tracks going across the ramp, and because it's a higher level it should go further back in the baseboard so as to not get in the way of everything else...
My considered advice is to ditch the ramp completely. The Midland did have level coal stages (e.g. Manningham, Lincoln), and some stages were later replaced or supplemented by more "modern" equipment, either a big full on cenotaph (mostly at the bigger sheds (or in the case of Hasland, ones not suffering from massive subsidence problems)), or a smaller arrangement usually consisting of an angled conveyor belt to raise the coal and deposit it in the tender using gravity. No doubt someone can provide photographs. The latter certainly would make an interesting model if animated. The key point is that such take up a lot less room, essentially being the length of a loop around an engine, and the width of about four tracks. Best thing might be to kitbash the Metcalfe kit into a level example, or there's a crappy superquick kit of a cenotaph.