🚀 go-pugleaf

Hi
Here's my question:
I have a PC clone (Teltron) 286 with 1MB of onboard 
memory, and I'm considering upgrading to 4MB.
I read the documentation which came with the computer
(poor documentation), but I found something which doesn't
seem logical to me.
The mother board is a Kouwell KW-241, and according
to the manual 1MB of memory can only be obtained 2 ways:
using four 256Kx1 bit and eight 256Kx4 bit DRAM, 
or
using four 256Kx4 bit and twenty 256Kx1 bit DRAM.
( I haven't opened the computer yet, but I guess it''s 
configured like that)
Still according to the manual, 4MB of onboard memory can 
only be obtained one way: using thirty-six 1Mx1 bit DRAM
(9 in each of the four banks).
Does this mean that if I want to upgrade I need to buy
4MB, not just three?   
If not, what would be the best combination and location?

Another question: I'm also thinking of adding a 2nd hard disk.
Now, I have a 20MB HD (don't know what type though).
The disk controller is an Everex EV-346, which according
to the manual supports one or two ST506/ST412 compatible hard
drives, and uses standard MFM encoding.
I bought Computer Shopper yesterday, but didn't see any
explicit reference ST506/ST412 compatibility.  I saw a lot of 
ST##### though.  Are there basically all compatible?
Also, can I only add an MFM HD? What about IDE, SDSI etc...?
Your help will be greatly appreciated.
Please respond to this group, or directly to me at:
6500erpa@ucsbuxa.ucsb.edu
6500erpa@ucsbuxa.bitnet