Enclosure for 2 or more millipedes

[Spidernoob2003]

I'm wanting to get some millipedes (specifically Spirobolus caudulanus and Archispirostreptus gigas) and so I'll be doing research to prepare myself, but I would like to know what size enclosures I can keep multiple of either species in as some sources say 5-10 gallons, but I don't know if that's for one or multiple. If you need clarification please let me know.

 

[Ratmosphere]

Never kept these two communally, but for my Archispirostreptus gigas I use a 10 gallon.

 

[Brewser]

10 gals allow for more wiggle room, 'the more the merrier'

 

[Spidernoob2003]

10 gals allow for more wiggle room, 'the more the merrier'

How many Spirobolus caudulanus could fit in a 10 gallon?