Since I'm planning to use a Lycoming, which is lighter than the Continental, I am relocating my battery and hydraulic pump to an area behind the passenger's seat. This is pretty much identical to the way John Halle's plane was done and his weight and balance came out fine. This also makes access to these items much easier than having them behind the baggage compartment bulkhead. Yeah, it takes up some baggage space but I still have plenty for my needs.
I cut an opening in the seat back then applied 4-BID to the rear of the seat back to make a flange so the piece I cut out is now an access panel. I then built a box behind the seat back by cutting and shaping 1/4" foam and applying 2-BID to each side to fabricate the rear, top, and sides of the batt/hyd box. I also used 1/4" phenolic to make a hard point for mounting the hydraulic pump to the rear of the box.
Image 1 shows the access opening with the hydraulic pump mounted on the rear wall of the box. The white styrofoam block is my battery model. It's not sitting straight in the picture because I haven't yet put anything under it to level it up. Later. The brownish area around the opening is the 4-BID flange. Later on I'll add nut plates or some sort of quarter turn fasteners for securing the panel to close the opening. The master solenoid and hydraulic pump relays will mount on the rear wall of the box above the battery.
Image 3 shows the rear and top of the batt/hyd box in place and the hydraulic pump bolted to the rear wall. I trimmed the control tube tunnel to clear the hydraulic lines, and to allow the pump reservoir to encroach slightly into the tunnel area. I did that to make sure there was enough room to get the battery in and out. I used 2-BID with a micro fillet on each side of the rear wall at the floor and where the rear and top pieces join. There's also 2-BID securing the top piece to the back of the seat.
Image 2 shows how it will look when the tunnel and end of the box are bonded in, which they aren't yet. They're just sitting in place to check the fit. (No, I don't know why there's a washer on top of the box. I'll have to check that out.)
I thought this might be helpful for anyone who would like to relocate their battery, pump, or both. If the builder is using a Continental and is concerned about weight and balance they might consider leaving the battery behind the baggage compartment bulkhead but moving the hydraulic pump up behind the seat. That shouldn't affect weight and balance very much, and will make it a lot easier to check the pump reservoir level.