You will probably see a bit of fat loss, and a much better over all feeling, but nothing for size. I ran 2 & 3 and got nothing for size, but could eat birthday cake twice a day and lose fat.
I have been running 4 iu for size for a couple of months and will likely kick it up to 5 in another month or two. Sad to say, but my lifting has really dropped off due to some other training, so I can't give a good report of what 4iu is doing...other than holding my size well in the face of a pretty good bit of physical exhaustion and a mediocre diet.
yeah that is probably a feasible dose for a pro, I wouldnt be surprised if he went higher, his slin dose seems low, my buddy whose a beast but no where near ifbb pro does 30ius per dose when he runs slin, yes its mainly genetics, but i guarentee those pros take advantage of their mendable genetics to the fullest and use as much gear as they can aslong as it keeps them growing