WHy would your neighbor be on top of you? It's not your responsibility to restore them for your neighbor's sake!

Maybe they shouldn't be 8 ft tall if they're in danger of being lost to wind and ice anyway. What about something different and maybe a bit more stable? Like a fence (to code. In bewteen property lines as opposed to front yard installation you're allowed to go a bit highter. From there come inside your property line a bit and install strong vertical supports in between each fence post placement...run a strong cable between those supports and plant wisteria. It grows abundant, fast, pretty and will add to the fence line in terms of height and privacy. It's just an idea.

If your neighbor is getting hot about the 'privacy' issue then let them put up their own hedges.

If you go the route of plants go to a whole sale nursery and look for things that won't be 10 times their planting width by the time they get to be 8 ft high. Lots of people have landscapers come in and throw any kind of evergreen or deciduous tree in along a property line; something destined to get 30 ft or higher and almost as wide.

That's what happened to the houses in our hood mostly built in the 1950's. They all have these massive evergreens about 2 feet from teh house or pushing up the sidewalks. Our neighbor had one of these monsters just tip over into the street onto the power lines after the last big rain storm because the ground was so soft, at the top of an incline and the roots might've been starved or messed up because of the sidewalk, utility poles and placement of two other trees of the same type and size on either size. one of those giants just had to be taken down last year from disease and the other one has roots crawling into my yard and it's not doing well plus the city comes by and mutilates anything that touches power lines.

Go to gasko's: http://www.gaskosfamilyfarm.com/

You wont find quality shrubs and trees cheaper.
There aren't too many plants that won't get too wide but will get very tall. Ask the staff there.

These blue italian cypress look elegant but again, how long will it take to get that high and what kind of maintenance can you realistically handle and somethign this tall and narrow will also be at the mercy of wind and ice.