A number of comments in reply (no order intended):

1. If you stick to GDAE tuning you can find a lot of written music and some software to use.

2. you can use either 'octave higher' or pairs on the base strings - your choice.

3. The longer the scale length the more stretch required. Personally I can't reach what I want to with any of the 25 inch or greater necks.

4. Citterns have 5 courses and mandolin family instr. have 4. Not a rule but a starting definition.

5. Now a personal comment. I like the 22 and 3/8 length. Why? I have a tenor banjo tuned GDAE (an irish idea, I think). Just got Blue star to make an electic 4 string roughly the same length. There are a number of 'octave mandolins' or irish bouzouki or mandola this length. Alternate you can get the 20 and 1/2? for all three. I like being able to go from one to the other easily. After I bought the ovation mandocello (25 and 1/2 scale length) I figure out most of this stuff. I still like and play it because it is a stong, powerfull battle ax. I tune it GDAE and it is a workout.

6. I agree with whoever said 'play it before you buy it.' I have also bought many before buying and now need to get rid of those that don't fit me.

7. Be prepared to play with string sizes in order to accommodate your direction.

8. Enjoy.