I know you are already aware that the guides are to wait until 6 months.
Even at 6 months the guidance portion sizes are tiny, a couple of teaspoons counts as a 'meal'. Although you might have seen a less hungry baby over night last night baby rice doesn't really offer much in the way of nutrition and his breast milk will give him more calories and nutrition than any solids can at this age. He might have felt 'fuller' due to the rice but might not take in as much in the way of calories as he would with breast milk only.
Guidance at 6 months is one meal per day, Tracy's introduction to solids from 6 months had 2 meals per day, it's here if you'd like a look:
Weaning Guidelines from Secrets of the Baby Whisperer(scroll down there for another helpful link with lots of suggestions of what to feed LO)
Then increasing to 2 meals around 7 months and 3 meals around 8 months. Later on when meals are fully established snacks might be added morning and afternoon.
Some find LO is ready for 3 meals earlier than these ages, it seems to be more common for BLW (finger foods only, no puree) to offer more 'meals' in the day but these are generally very small tastes, LO self feeds so can only eat as much as they can get in their own mouth which is often not very much, licking and sucking, learning about tastes and textures is more the focus rather than 'eating'.
The important thing with either the puree route or the BLW route is that the milk intake does not drop at all, solids are in addition to milk and do not replace any of the milk feeds.
I would try to hold off on solids for a few more weeks and perhaps use that time to look into the benefits of finger foods. In the UK now the advice is to either skip puree altogether or if purees are used to also introduce finger foods at 6 to 7 months. Learning to manipulate food with their hands is great for fine motor development and manipulating food in their mouth is great for speech development, plus baby leads on how big the portion is so they are not coaxed into eating more than needed. I found with my DS he even appeared to have an inbuilt ability to balance out his food groups, I was amazed, he knew when he'd had enough carbs and wanted veg for instance or how much dairy his body needed. Worth looking into IMO.
Here's a link if you are interested:
Baby-Led Weaning