These are my solo rules. They look pretty complicated but it´s really not that bad. After a few turns, the game should go fast and smooth.
Solo Rules for Space Hulk
You always play the side of the Space Marines. There are no rule-changes in the Space Marine actions. I don´t use doors in my missions.
The Line of side ends after 12 spaces (it´s getting to dark)
There is a maximum range for all weapons of 8 spaces.
On crossings check the movement direction of the Genestealers
First target is the closest group of Space Marines (a). The Distance to this group is α.
There might be other groups b. Their distance is β.
If β ≥ 2α, the Genestealers (g) will go for a.
If β < α roll: on 1-4 g goes for a, on 5,6 g goes for b.
You check on each crossing they pass again, for wich target they´ll go. They will never turn around and move back.
On a crossing, they prefer to take the shortest way (Ws), when going after their target. If there is another way (Wl), wich is no more than 8 spaces longer, roll.
1-4 g go Ws
5,6 g go Wl
Attacking and lurking:
A blip/Genestealer might stay lurking behind a corner.
G attacks always, if the Space Marine can´t avoid close combat.
Distance to Space Marine is d.
If Space Marine is or could go into overwatch (due to command points) and shows in the attacker´s direction:
If d > 5 g only attacks on a 6
If d = 4,5 g attacks on 5,6
If d ≤ 3 g attacks.
If the Space Marine is not in Overwatch and can´t go there or shows not in the attacker´s direction:
If d > 10 g only attacks on a 6, if no 6, g moves until d=13
If d = 9,10 g attacks on 5,6
If d < 9 g attacks.
You make these checks again in every turn.
If there is more than one blip around the corner and the gap between the blips is <4 at the beginning of the turn, they will always attack!
The Genestealers always move simultaneously, i.e. if a group of genestealers moves and you kill the first one, the following one is then in the space right behind and would so move with the next action on the space where you just killed the other one.
To make things easier, if you move big groups of Genestealers, simply place the last one at the front (just remember, it´s still the same target you´re shooting at.)