Hi there
Would he do a slightly longer A time before his afternoon nap? He looks to be doing 2.5hrs following his 1hr am nap, which is quite short for an 8 month old - maybe you could try increasing it a little say 5-10mins every few days, with the aim to eventually push that 2nd nap towards 1.30pm? Might give you a longer nap.
HTH.x