If you put a strong player together with a weak player, the opponents will (should) hit to the weaker one. Basically, you are only as strong as the weaker player.
If 1 is weakest and 6 is strongest, try--
6+4= your number one team.
5+3= your number two team.
2=1= your number three team.
This will give you an overall blending of strengths/weakness in the top two positions.
Also consider, simply putting your two top players together, the middle two together, and the lowest two together-- This may give you the best arrangement to win two of the three sets.
There is no point to having the least good players play out of the bottom position.
Also, consider setting up practice sessions where your better players help the weaker players improve their game.