Why a Reverse Valve Body?

There's some partial information here... Sorry, it's wordy...lol
The main reason for the manual shift cretion as I understand it was quickening the shifts. Reversing the passages for first gear vs third shortens the fluid path between 2nd and 3rd and also removes the possibility of 1/2 shift overlap when the low/rev band is applied in factory stock manual low gear. Mopar calls it "Breakaway First" when you place the trans in "1" with the gear selector. In a factory valve body, engaging "1" engages the forward clutch pack and the low/rev band. The band backs up the sprague, or overrunning clutch, in break-a-way first. It should be noted the sprague is the only fixed (not fluid activated) holding component for first and second forward gears. It does not hold anything in third. Inside the valve body, the fluid has to go around a maze of casting to get from one shift valve to another before it heads out to the various servos or clutches. So no matter how much you want to speed things up in terms of 3rd gear activation, you can't unless you shorten the distance between the shift valves. By reversing the path that fluid taes throught he valve body, you quicken the response time to the shifter input. When we drill the casting with that special jig when doing adding shift kit, we're doing a similar thing. Bear in mind we're talking hundreths of a second but if the trans slips for .05 second at full throttle every time you upshift, after a season that friction is trashed. So the trick is no overlap, no slippage. that's the "why" behind a reverse pattern manual valve body.
On the tranny explosions...
Now because the typical (Cheeta, DC tech papers) valve bodies do not use the band in first, the risk of messing up the sprague is inreased. It can be damaged when the tire speed is faster than the engine speed (like if you let off during a burnout in first or second instead of powering out or if you slip the tires in the rain and let off the gass to let them "catch up"), or when the force through the sprague is interrupted like when a rear shears teeth or fails. So they call them not for street use. The way to minimize the possibility of explosion due to sprague failure is to buy the "low band apply" manual valve bodies. Cope sells a good one but there are others too. Some are forward (factory) pattern, some aren't. All they will do (at teh expense of the ultimately fastest shifts) is apply the low/rev band in first. They dont help with the sprague in second. They dont stop the explosions simply by using them. That's because to stop the explosion, you have toreplace the explosive...
The factory forward clutch retainer (that means forward in the case, not forward gears, because it actually is engaged in reverse too...) is a powered metal manufactured part. It's light and cheap, and plenty strong. When you read about "adding clutches" or the "Hemi band and clutches" thats the part that is different. The problem with the powdered metal drum is is cannot safely spin beyond about 8K rpm. Normally, because it'sonly used in 3rd, it would never spin that high. However, in first gear, there is nothing holding it still except that rear sprague. And it's held through a series of mechanical gears. So, if the sprage fails, the gears in the connection begin multiplying the engine rpm as it's applied to the drum. When the engine's at 3K rpm (like foot braking the stall, or on the trans brake, or just as you let off the brakes on a street car) the drum can be spun to over 12K rpm. It explodes around 10,000 rpm, and the force is the same as a stick of dynamite surrounded but steel. The way to permanently fix the explosion deal, and remove the risk entirely, is to have your transmission built with a billet steel or aluminum forward clutch drum. Then you can still break the sprague, but you wont lose a foot, rip the unibody apart, or kill a spectator if you do.