Looking at the picture above /\, I'm not sure why you cut the whole rear package tray out? That's allot of work to put it back in, and because its old steel, now you will be chasing body cracking.
Plus I suggest you build your lower main rail first before building the rest of the cage (Lower tube from beam to torsion housing.) Then the rest of the cage is built off that lower tube. (Think buggy frame)
Regarding Electric PS, If and when I build another car, I will be looking very close at using electric PS. My UTV has it, and have considered converting my current prerun Baja to it.
On my last Baja play trip we were having dinner at Jardines in San Quentin and there was a rally nice 2 seat a-arm prerun buggy (ecotec engine) with 35" Baja TA's in the rear & 35" MT Baja Pro front tires. After talking with the guy he said he had electric PS on his prerun buggy. He had got tired of the Hydraulic PS issues (Two failed pumps in two trips was enough!) and converted his car to Electric PS. He said its been one of the best improvements he has made. For one he eliminated the pump, lines, servo, power ram rack, reservoir etc.. Two he said even if the electric unit failed or was turned off you can still steer the car, just like a non PS car (This is true as its the same way on the utv) so your not going to crash if it craps out or locks up. I'm not sure how it worked but he said his unit had a control box with a dial where he could adjust the speed and amount of feedback the electric unit made? He was saying he had a few thousand Baja miles on his car with the electric PS and has had zero issues. Plus the whole system installed was much less then what he had paid for his Hydraulic kit. He said he bought his Electric PS as a kit from a guy who makes them up, and said the actual PS unit was a GM unit. He thinks its from the car platform, like the Chevy Cobalt, Cruise or Impala. The other prerunner with them said they too were impressed with how well it worked and if he was to do it over, he too would do Electric PS.
And like Wilson said above; most 5/1600 guys end up using the Charlynn set up, as it easier to make work, but on our 5/1600 we did the Ram style and was able to make it fit and works great. We stayed within the 1 inch pan rules and have our rack dropped as far as possible. So its do-able. Its just allot of time and hard work, but like everything, if you take the time and work at it, you can make it work. Just got to think outside the box of what everyone else does.
Regarding the brake master cylinder, back in 2001 we were running the duel circuit master cylinder with duel CNC brake fluid reservoirs, when most were running the Single Bus Master cylinder, with plastic reservoir. Our theory was like what Wilson said; you wont lose 100% of your brakes if you have a failure at one wheel. Back then you had to run drum brakes and master cylinders could fail and wipe out your brake shoes too. When the rules changed and we could run disk brakes, we looked and found a place that could machine & rebuild a duel circuit master cylinder to accommodate disk brakes. At the time no one was making aftermarket stock masters for disk brakes. This was just one of those small details that made our car so advanced for its time.
The Negrete Boys have invited me to go along with them and co pilot for a stint in their car. I'm just a little excited.