garbage disposal plumbing problem

I ran into a problem when I was trying to install a garbage disposal (there wasn't one before). Waste pipe entering the wall is a little (about 1/4") higher than the disposer discharge (centerline to centerline). If I install it like this, there is going to be standing water in the disposer. Is this a big problem?
This is a small unit (1/2 HP). I looked at other vendors, and it seems like distance from bottom of sink to centerline of discharge outlet is pretty much the same for all of them (6"). (Surprisingly they have so much in common - including the pictures in their manuals - I suspect there are only a couple of manufacturers out there).
I can't replace the sink or move the pipe entering the wall. Any suggestions? Are there any brands out there that are shorter or have different designs?
Thanks a lot, Matt

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