DEC PDP 11/23 - OK to use 22-bit memory boards in an 18-bit qbus?

Hello, I recently acquired my first DEC PDP. It is a VT103 (VT100 terminal with a PDP 11/23 inside). It came with a pair of cartridge disk drives (HEAVY!) that are RK05 compatible, a DEC RX02 (pair of 8" floppy disk drives), boxes of manuals, 3 DEC operating systems, software, and an extra VT100. While the DEC operating systems are OK, I am actually interested in using the machine to (finally) go through "Lions' Commentary on Unix" (Unix V6), using software downloaded from http://www.tuhs.org/. (Lions' book here): http://www.amazon.com/dp/1573980137/ After I do that, I want to move up to Unix v7, 2.9BSD, and try other Unix distros available for the PDP. My concern is that the 18-bit PDP 11/23 does not have enough memory. It currently has 128KB installed, with a maximum of 256K possible after a memory board upgrade (M8067, MSV11-PK = 256KB). How far do you estimate I can get with just 128KB memory? Can I get through Lions' book? I am looking at adding wires to the backplane to make it a 22-bit machine, and using a quad height qbus memory board, M7551 (available in 1MB, 2MB and 4MB sizes). However, I am not ready to dive in and start modifying the qbus backplane for 22-bit addressing just yet. So my question is: Rather than invest in a 256KB memory board designed for the 18-bit qbus, can I install a 22-bit 1MB, 2MB or 4MB memory board in the 18-bit system, and just use the first 256KB for now? Also, is the VT103 backplane compatible with a quad-height memory board? (It only has dual-height cards installed at the present time). Parts inventory: - VT103, with: - 4x4 qbus backplane, 18-bit. The manual says "two H803s (2x4 connector blocks, stacked vertically in a 4x4 configuration)". I know there are possible issues with "straight" vs. "serpentine" slots, but I have not got that figured out yet on the VT103. - M8186 KDF11-A CPU (Newer revisions of KDF11-A's are 22-bit capable). http://world.std.com/~mbg/pdp11-field-guide.txt says: "(Prior to etch rev. C, 18-bit addressing only. ...)" I could not find revision information on the M8186 board, but "146 CA" is stamped into one of the red plastic handles. I can email close-up photos to anyone who wants to take a look and determine if this is a rev C or later board capable of 22-bit addressing. - M8043 Quad Serial board. This doc says it is 22-bit compatible: http://www.ibiblio.org/pub/academic/computer-science/history/pdp-11/hardwar… - M8029 (RXV21) floppy disk board (18-bit DMA only). -Will this be a problem with Unix v6 or 2.9BSD if running with 22-bit addressing? - M8208 "VT103 Maintenance Module" (Unknown if 22-bit compatible). - Xylogics C510 (formerly called "Wizard 1") cartridge disk controller board, with 18-bit addressing, connected to a pair CDC 9427H "Hawk" disk drives (one disk drive is DOA, but the other is OK). - 3rd party memory board (128KB), Christlin Industries, Inc. So, initially I want to run a 22-bit memory board (M7551) in an 18-bit VT103 qbus backplane, and access only the first 256KB of memory using 18-bit addressing. Is this possible? Thank you for your help. Scott M.