K.E.
My middle son also went through a period of two very short naps. His older brother actually slept more than he did! At some point (maybe a little over 1 year) he started sleeping longer in the afternoon.
I agree with others that you should give up the third nap, but otherwise just keep doing what you're doing. He'll probably shorten the morning nap on his own soon enough. At only 8 months, I doubt he's read for just one nap yet.