GW generally sculpt to heroic scale, something we see a lot in comics and computer games, which is usually over sized muscles and, in the terms of women, very curvy. We sort of see this in movies, with perfectly sculpted men and women who would need to spend most of their days down the gym to achieve such results.
For Space Marines this is fine, they should be oversized. The problem is, GW sculpted their human models exactly the same, so your Imperial Guard grunt is the same size, although slightly less bulky, then the genetically enhanced Space Marine. When they brought out the plastic Space Marines, they did make them slightly larger, but gave them bow legs which brought them down to the level of human models, later plastics have addressed this, and Forge World tends to have better poses, and are sculpted to a more realistic scale. Also, newer Imperial Guard kits, particularly the plastic storm troopers, are smaller. But even with these changes the height differences is not enough.
So the art of 'True Scaling' has developed. There are several methods to achieve this. The first, and one I have been practicing for a few years, is to add plastic spacers to areas of the body. Depending on the result, you could add 1mm to the thighs, and the waist, or you could add, it to the lower legs, upper legs, waist, neck, and even use it to make the torsos bulkier. I usually think it's enough to add to the legs, waist and neck. This is fairly easy to do with plastic models as plastic cement does a really good job of bonding the spacers to the model. With resin models I find it requires a little more patience, as the superglue needs longer to creat a good bond between spacer and model.
The above has had 3mm added to it.
Now this method gives the model a slender, more human look and it removes the heroic scale for a more natural one. The second method adds both height and bulk. This method involves taking terminator legs and converting, by sculpting armour, them to resemble power armour. This also requires a lot of work on the torsos to get right, and also involves making new shoulder pads to fit the larger bulk. I don't have any example of this, but google Doghouse, Apologist and Migsula to get an idea of the effect.
Recently I have realised there is a middle ground, take terminator legs, particularly the new ones from Forge World and the newer kits from GW, cut off any part above the belt, then add a normal torso, and fill put the waist with pouches and grenades to add bulk. This is very simple but effective, and while experimenting I decided to take it a little further and add some height to the waist. I then sculpted the missing detail, added some of my own, and was finished. I think the effect is impressive, the model is larger and bulkier, then the original models, and the spacer style truescale.
The height and bulk of the model is created using terminator legs, some green stuff, and the extra gear on the waist.
I may further refine this method, add a little more fight to the waist to get an even bigger model, but I do feel this is on the right track to creating a space marine that fits the background. Lastly a scale shot, plastic imperial guard on the left, forge world space marine, spacer altered space marine, and lastly the newer truescale attempt.
