@George Lods
You can always request a rent increase however it's not always met. S8 department has their own way of figuring "market rent", wrong or right. Generally trying to make the tenant pay more of they portion is difficult and doesn't happen too often.
What you mention of S8 not paying full mkt rent is very true. If the rent works out in the low 700's as opposed to $800, then its okay. It matters when you base your numbers off the $800 and S8 only offers $700.
For the units I have that are S8, I NEVER worry about payment. ALWAYS on time (unless holiday).
My expericene of S8 (5 years) is that the tenants are LONG term. So whether they are S8/F.responsible, after the long term tenancy your going to have to do a turn over regardless.
Depending on who is doing your tenant screening (assuming all laws), whether its your or your PM, apply best judgement possible...just as any other tenant.
Im sure you will require a deposit, so it goes the same for S8 tenants and f.responsible tenants.