Usually the 3/8ths" or 1/2" disks work fairly well with motor conversions. (as well as "usually" being the sweet spot for N40/42 disk neos in price)
You can stack them for more depth easily.
Check your formula in the cubic inch columns--something seems amiss there.
As well as the total surface area column formula--only one side (N or S) is actually doing the deed in most configurations we/us/you normally use, but since a mono-pole mag doesn't exist yet in any effective quantities we just use the other side to help stick the mag on some steel or another mag if stacking them until the sticky stuff sets good.
Stacking 2 or more mags on top of each other just has the same (one side--effective area) surface area as one mag has "exposed" for "fluxin" the wire coil(s).
Most of the time you can forget replacing any of your mentioned already "PM" type motors with neo mags--they will cogg after and won't make many more watts even if rewound. Rewinding those really small motors isn't easy and usually produces a result of mixed feelings--i.e.--success/it sucks for final results. Find a bigger motor with real ball bearings and maybe at least a 1/2" shaft to mount the hub/prop on, and bolts to hold the frame/motor together instead of welds/pressed.
It isn't hardly any more work (probably less) to convert a 1/4hp or larger (don't go nutz on the first one as to size) single or 3 phase motor with neos and no rewind of feild coils, then jack around with a window fan, or even worse, a vacuum motor that requires 11 gazzillion rpm to make 8 volts and is very dissappointing in the end.
Servo PM motors are a distinctive seperate subject apart.
Hint--read/search lots of "zubbly" on this forum, he's da man on converts, as are several others (dinges, etc) that have been there and done it right..(are reasonably happy with results that is.)
/me Inserts disclaimer here---
All of the above is personal opinion mixed with some experience--this and $.50 should still buy a cup of coffee somewhere, maybe, possibly.
