Tyranids defending in Crucible of War

[polkadragon]

As the title says, my Tyranids are going to be the defender in the Crucible of War mission.

I'll have 1700 points at my disposal, but can only take 1 elite choice (remnant from previous campaign battle)

I've never had an Imperial Bastion at my disposition before, so I'm looking at army list ideas on how to best use this as a Tyranid. My current idea is an Old Adversary Hive Tyrant at the centre and as many devourers around him as possible. Hold the Swarmlord close for Psychic Support and a devastating counterattack. Hide Biovores to pound his approaching troops.

I also have the option to give one troop choice the Stealth rule, so If I put for example 18 Devilgants in the Bastion they'll have a 3+ cover save. But how many will be able to shoot out of the fire points? Is this a good idea?

This is current 'working list' , I appreciate any insights!

The Swarmlord 340
• 1 Tyrant Guard
Hive Tyrant: twin-linked devourers with brainleech worms; twin-linked devourers with brainleech worms; Old Adversary; armoured shell. 265

3 Hive Guard 150

The Scuttling Swarm Tervigon: Catalyst; cluster spines; adrenal glands; toxin sacs. 195
The Scuttling Swarm Tervigon: Catalyst; cluster spines; adrenal glands; toxin sacs. 195
10 Termagants 50
Stealthgaunts (18 Termagants): devourer. 180

3 Biovores 135
1 Carnifex: twin-linked devourers with brainleech worms; twin-linked devourers with brainleech worms. 190

1.700 points