Why on earth would you want to plant a Cleveland pear? One of the worst choices imaginable.

Dan

I would rather get an answer than a negative comment. No more of those please.

I'm not going to give you a negative comment but I just want to point out that the reason you may likely get negative comments are not because people are upset about the pears being prone to breakage. There's plenty of trees that are prone to breakage or short lived that are recommended here. But the reason people will be irked with you is that you are adamant about planting an invasive species.

To answer your question, these won't make a good privacy screen since to take advantage of the slightly improved crotch angles, you will need to give them enough room to develop a strong branch structure. Planting them close enough to screen a view such as done with common evergreens like leyland cypress, is going to cancel out any benefit.

You asked do you think 9-10' will give you the privacy screen... the answer is yes, for a brief while. I say brief because the trees will not do well that close together and you will eventually be back at square one.
Furthermore it sounds like it's going to shade out your crape myrtle. Those do best in full sun and in nj where you're pushing it with those to begin with, planting one 8' from a callery pear is basically giving it a death sentence. Certain trees require full sun and adaquate space to grow. Unfortunately, you managed to pick two such species for a privacy screen.

I also think 10' will be correct for the Cleveland's.

In West St. Louis County there is a neighborhood which has an interesting screen made of Clevelands and some kind of long leaf pines. The Pines are being out competed and don't do their part over the winter.

We're talking maybe 60 Clevelands here! Sure some have done their thing and split causing fence issues but hey, they're not big enough to fall in the street and kill folks.

Here also in Z6 I have a Crape Myrtle planted for my wife. Its a cute flowering upright bush. Its pretty darned late to leaf out though. Being NJ near the ocean have you seen a number of Crapes doing well in your neighborhood? I know they like sun. If you plant it on the south side of the Clevelands where it casts shade on the Pears it might do well.

Far as the invasive issue, if you're willing to spend the time plucking the seedlings all up go for it I suppose. Think about the uproar if I brought in a lot of xxxx into your neighborhood which replaced your beloved yyyy's

Here is the positive spin:

You want to make a great choice in your tree. A great choice includes many great trees. Congratulations on your great choice that doesn't include non-great invasive species and suboptimal branch structure and less-than great appearance after the great storm makes the pear less wonderful by goodly breaking out 1/3 of the wonderful crown and reducing your beloved privacy.

HTH.

Dan

If a tree breaks it is a problem for the owner but if it spreads in to natural areas and becomes an invasive species ousting native flora, then its everybody's problem. I believe that is the main reason Cleveland pears have a bad reputation.

@tulln1: how did your trees work out? by now, there are somewhat mature, yes?

see my post The Coming Plague of Pears. New posters here would be well advised to take the advice from the rest of us. OP was from NJ, I am from Maryland, callery pears are some of our worst weeds. We have so many superior trees, why plant these weeds?