Here’s two pictures how to modify stock rev2 to use 2716 eproms on full capacity.
You’ll need to remove the voice board (board 4) to get access to CPU board. Refer to Rev2 technical manual for further dissassembly instructions. (Rev2 tech manual is downloadable on synfo.nl)
First you’ll need to install two wires from Eprom 0 socket. One goes from pin 19 to CPU pin 3. This enables addresses at $2000. Second wire from pin 21 goes to pin 24 of same socket. This ties pin 21 to +5V.
On component side two tracks to power supply needs to be cut and two ceramic capasitors removed from address lines.
It is possible to use 2816 eeproms with same modification (/WR is tied to +5V). Using eeproms is quite handy – there is no need to use UV erasers when updating new binaries to eprom sets.
You can also use stock v6.0-7.0 binaries on 2716 eproms with this mod. The A13 line stays on logical 0 this way too.