Portacot use for bub while trying to transition


Not sure if this is a silly question but would it be bad for bub to sleep in a portacot at night for a few weeks? I know the mattress isn't very thick so i didn't know if it would be bad for their back. I'm asking because he currently sleeps in our bed and i want to transition him to his own bed and he has outgrown his bassinett already (he's just over 3 months old). His room is at the other end of the house so I'm not comfortable having him that far away yet. He has always needed to be sleeping on someone or in bed with us in order to sleep but i decided to set the portacot up in the lounge room to see if i could start getting him to have naps in there and he seems to like it. He still only sleeps for approx 30 mins but having him to sleep somewhere that's not my shoulder is a huge step. Do you think it would be ok to try and start putting him in the portacot at night in our room until he's ready to go into his room or are they only suitable for short sleeps?