Well I finally bit the bullet and bought a aluminium backplate.
I was looking at the diverite one as it appears to be very good value for money, however in the end I went for a OMS plate.
Assess what you are planning to use it for and then consider the options.
I am planning on using mine for holiday dive (nice and light for travel) and also use with singles and the OMS plate has slots for cambands the diverite one did not appear to have slots so I would have required a STA. This was the reason I choose a OMS over the diverite.
The OMS one cost me £50, I think the diverite one was about £40. After I added on the price of a STA the diverite one would have been more expensive (and I guess I would of ended up with a stainless steel STA?)
Also the OMS plate does have a very flat profile and slim groove.
(I did look at the Halcyon plate as well, for about the length of time it took for them to tell me the price
)
Daz