advice on setup and rules for a 5x6 game of minichess?

Hey, all.  I was wondering if you could give me some feedback?  I'm writing a minichess program for the iOS/OS X and I am considering what would be the best initial setup of pieces.  If you are unfamiliar with minichess, there is a wikipedia article  Wikipedia: Minichess.

I have decided to implement a 5x6 variant with a KQRBN back row (not necessarily in that order).  Instead of just choosing one set order for the back row, I have made it random.  Well, semirandom. 

The way I am currently setting up White's pieces is I am starting with an normal 8x8 white back row.

RNBQKBNR

Then I am randomly eliminating on of each of the paired back row pieces.  For example, this would be a legal back row for white via this approach.

RxBQKxNx , which would yield a back row on the 5x6 board of ....

RBQKN .

While semirandom, I like this approach because it maintains some of the inherent relationship of the back row pieces that you see in regular chess, such as rooks starting in the corner, bishops adjacent to either the Q or K, and queen and king adjacent to each other.

The black back row then is randomly set to be either an exact mirroring of the white back row (as in full chess) or the exact reverse order.

I like having the 50/50 chance of a reverse ordering because it increases the variability of the board but it gives me qualms to have a setup where the black king is on a lower file than the queen. It is not a completely novel idea though as both the 5x6 variants Speed Chess and Elena Chess (see the wikipedia article) have this relationship.  What do you think?  

The alternatives would be to no allow a reverse black setup (bleh) or to allow a reverse setup, but to keep the expected orientation of QK.  I'm currently not favoring the later approach as it would lead to some very asymmetrical board, with, for example, one player starting with a queen in the corner and the other not.

Other rules questions are should pawn double moves (w/ en passant capture), pawn promotion and castling be allowed?  My current implimentation allows double moves and promotion.  Castling is allowed, but only if the queen or king start in a corner (which would mean that castling would be "full sized").

Well, what do you think?  I am far from the first person to try to come up with a good setup for a 5x6 minichess game.  I would love any feedback from this forum on setup, pawn movement/promotion or castling in this type of chess variant.

Tiny Chess

why not 6x6?

In the 60s I played a 5x6 variant called 'quick chess', simplified chess for teaching. The rules were randomly place R, N, B, Q, K. (120 possible starting positions) No double pawn move, no castling.