As delivered, Diesel measured (in mm) 168H x 115W x 324L but its wheels appeared to be undersized and the running plate too low, which also appeared to exaggerate the length of the overhangs at each end. I thought it looked a bit weird.
To sit comfortably with my existing rolling stock (and track) I needed to cut 20mm off the height and 12mm from the width (from the centre of the body and 6mm plus from each side of the supporting chassis moulding). To adjust the proportions to more like a Class 08, I then needed to lose a fair bit of the length too; say 20mm plus, off both the front and rear overhangs. Helpfully, the original cab appeared too long anyway, so building a new, shorter cab wasn’t a problem.
I was limited in where I could remove ‘featureless space’ from the body sides, so the front overhang wasn’t touched (and the wheels are still too small, of course) which makes the revised version look, perhaps, a little long in proportion, with roof sides that aren’t as steeply pitched as you’d expect from an 08 (see above).
I’m sorry, this answer is probably unnecessarily long, detailed and tedious (but I’m not writing it again).