advice on kitten to resident introduction

[u/sk2001_]

so i brought home a stray 4-5 week old male kitten. i have a resident former stray, 3-7yo male neutered (no idea how old) who used to live outside as a male tom cat breeding for england & lived with lots of the other outdoor strays. he’s actually the most chill cat i’ve ever had and so was hoping introducing would be ok.

i’m on day 5 - kitten is in a pen as is too small. fred my resident has seen and interacted with the kitten through the pen on several occasions (he barged his way in the bedroom on the first night despite me shutting him out & crept up on me in the kitchen when i thought the door was shut) and we have only had hissing, no growling or spitting or aggressive behaviours. we do breakfast with them together each morning as we have had positive outcomes (bert the kitten eats in the pen, fred eats at a distance but in the same room) and he’s been fine. they are separate majority of the time, only when myself or my partner are home do we try and do small interactions and scent swapping. they are never unsupervised and haven’t yet met face to face outside of the pen - i won’t be doing that for a while. i’m trying to do short bursts of positive interaction & then let fred chill and acclimatise. i reward with treats when he is chill and has positive non hissing interactions with bert (bert the kitten)

this evening we had bert in the pen in the living room and fred has been sat on the sofa in the same area - hissed at me once & has hissed at the kitten when walking past but otherwise seems kind of neutral. no real emotion towards the kitten being there other than distaste lol

i’ve never had to do kitten to adult introduction and feel like i don’t know what i’m doing. i’ve introduced several other cats in the past but they were adult to adult.

is this all ‘normal’ and should i be concerned? is there anything else i should be doing? i feel like im doing things wrong & im not sure how to tell if its going well or not :/ just need some advice pls xx