I rebuild mine to take a full years worth of ME in each binder and a similar fill of MEW (30 months ish) in individual transparent ring binder wallets. The bumper pack ones sold by Woolworths being excellent value and stronger than many, naturally I stocked up during the closing down offers at the local Woolies. The edges of the wallets project slightly from the binder covers but I don’t find this objectionable.
Method is to fit a shallow, flat bottom, U channel bent up from alloy to the spine in place of the standard wire carriers using 3 mm screws and nuts through the wire carrier rivet holes. The U fills the full internal width of the spine so the binder sides point straight out, the curved back MEW binders get pulled flat during the process helped by an extra screw in the middle. The shallow sides are drilled at 4 hole ring binder spacing so that short tubes can be held in place by countersunk self tapping screws. These tubes support the wallets. I put 3 or 4 extra wallets at each end for use in case of catastrophe. Kufnier brake pipe tubing, left over from a full roll obtained mumble-mumble years back to sort my GT 6, works well. Uses up the box of small 6 mm long, 3 mm diameter C/S screws you get with the Screwfix Gold pack too.
As I have a full set of MEW and my ME collection goes back to 1972 the halving in shelf space needed for the A4 and previous size ME issues is worth while. The old, small, ME go a year to a binder anyway. Not so welcome is the collection of redundant wires.
A production version of this system would be worth considering if changes to the official binder are in the offing.
Clive