yes to karl foerster
yes to panicums (especially heavy metal for narrowness)
yes to helictotrichon (doesn't get very high...in fact it is wider than high....very nice though)

You might find some muhlenbergia varieties to your liking. Muhlenbergia do well in California, so in Italy I expect they would also do well.

Miscanthus are pushing your width restrictions (but morning light is a very nice grass....take a chance) & I don't grow pennisetums so I have no opinion on those.

ciao.

Thanks DeepRoots!
I've googled on Muhlenbergia and found M. Capillaris that looks simply fantastic. But the Italian website where I will place the order doesn't have it in its catalogue. If someone know of some online sources for OG's in Europe please let me know.

My Karl Foerster is about 5 feet across, but I did neglect it for some years and now I need to redo it. Keep after it and you can keep KF in tow. Heavy Metal is less spreading for me and is modest compared to KF. I also have another cultivar of feather reed grass called 'Overdam.' It is quite compact, and has variegated blades as a bunus. I am 6'2" tall and can see the seed heads at eye level, but the screening might not be what you are after even at that.. the dense part of the plant probably tops out at 3-1/2 feet. Very tailored, and might be good for your situation (even after 10 years since your posting. ;-)

I can add an enthusiastic endorsement of Panicum Heavy Metal. It is very vertical, doesn't tend to flop at all, and is way easier to divide than Miscsnthus. I live in Northern California, UISDA Zone 9, and we have a long growing season. Miscsnthus varieties are very vigorous in my garden and they have deep roots. When they get big, they are really a big project to divide. Still, they are gorgeous and if you have the stamina to do so, divide them frequently, maybe every year or two to keep them the size you want.

Pennisetum is my favorite grass (or is it Calamagrostis foliosa)...

ive been growing Pennisetum alopecuroides for perhaps 30 years, first the species, then the smaller Hameln. I find it an indispensable mixer at the mid-size level of the garden. It has almost 11 months of interest in my California garden. A fine textured mid green in summer with an extremely graceful fountain shape, then it bristles with pretty flowers in late summer. Then in fall, my favorite season, it turns all shades of straw and russet and brown, gradually bleaching out to straw as winter comes in earnest. But it holds a nice shape and has "presence" until it needs to be sheared to a few inches from the ground here in late January. In milder winters it will start to grow in early February and it isn't long before it is looking really pretty.

High Country Gardens sells one called 'Thin Man' Indian Grass. I love this grass!! As described, its stiffly upright, thin and blue, mine is just now blooming. They had limited quantities last spring and are currently out of stock but hopefully will offer it again next spring. It was developed at the Los Lunas Plant Research Center. I found very little information online but ran across this photo showing a progression of growth.

Have you tried zebra grass? Also named Miscanthus sinensis..Ive got about 20 plants in my yard.Went from 5 to 20 by dividing the 5 this past feburary.They all are doing great.Some are bigger than others(richer soil)Right now they have the tall shoots on them(see pic)..The only draw back is when they get the shoots and rain they tend to fall because of the weight

Going back to your original concern, how wide do the grasses in your list get, it is wise to remember that all grasses get wider every year, so really vigorous grasses will need digging, dividing and replanting more frequently than less vigorous grasses, both to look their best and to keep to their spaces. I, too, have a small garden and I have eliminated Miscanthus from my garden because of its vigor and the big chore they all are to divide. The same with most of the many beautiful Muhlenbergias. But, OTOH, if you have a strong back, or a good gardener, then it is only a matter of choosing the grasses you like and keeping them to the design or aesthetic size you want. Some will just take a little more frequent work than others.