@ lele - is ur bonbebe freestar 'spacious'? if it is, i'd think tats the reason its causing ur boy to slide to one side.
my bb 1st used a Combi stroller when she was born, till abt 3mths. returned the stroller to a fren when his wife got preggy again, & bought an Inglesina pram. as Inglesina prams are more spacious than Combi's, bbs tend to slide to 1 side when sitting/reclining more upright.
Tho' Inglesina prams are heavier than Combi's, i prefer Inglesina as they're sturdier. When going up & down escalator, no fear of ''tripping' when nearing the end; unlike Combi if its turned to face mummy. Also, Combi being lighter, is more 'cramp'. So bb won't be able to use it when they grow bigger, else their shoulders will be 'squeezed' tight.
My niece who's being using Inglesina since birth, is still using it. She's nearing 3yo, & is already 21kg. Pram still going strong! Darn gd buy.