I know this cabin so well!

I prefer aisles to windows. Did you want a window? And one with a view? For aisles a D/G near the back gets you the best chance of an unoccupied seat next to you. But some people complain about the AVOD box taking some of the foot space.

I would still get them to record a request for 20A/K or whatever you want.

On my last sector - BKK/LHR, there were only 2 diamonds and 2 golds on the entire plane - all in Elite! (Don't know about silvers.) I was in 20H, the other diamond in 26C. The golds were in 23H/K and 24C.

20AC were unallocated, and somebody asked if they could move up. One guy was in the centre block. They blocked 20K for me.

So I think requests stand a good chance.

One more thing... the front of the Elite cabin is much warmer than the back. I've often thought about taking a rear seat just for somewhere cooler.