Hello yes I do mainly feed chicken mince 300g a day sometimes liver and once a week a tin of sardines this us mixed with sweet potato or brown rice, green veg, carrots beans or whatever veg available he has some treats kibble type through the day when training etc also some blueberries, apple slices ocasionally when I said lean, he looked good in at the waist a little bit he weighs 12kg a week or two after changing him to kibble his tummy goes rounder and from back looks slightly round each side perhaps slightly bloated I am too squeamish to give things like lamb spines chicken carcass etc so perhaps if the mince is not enough perhaps a good quality kibble is the way to go
300g raw meat for a 6 month old pup weighing 12kg is only around half of what he should be getting. The link I've posted at the end of this post will help you with how much he should be fed and the types of food he needs. At 6 months and weighing 12kg he should be fed around 600g of raw meat per day. Any veggies that you add should be seen as an extra rather than an essential part of his diet, and he doesn't need rice at all.
Most raw feeders aim for a balance of about 80% muscle meat, 10% bone and 10% offal, of which half should be liver. Bone is essential for calcium, especially in a growing puppy and he really needs it in his diet, If he's been without calcium in his diet for some time you're putting him at risk of not developing properly. He should also have much more variety in the meat that he's being fed. Different meats have different protein levels and nutrients, and variety is one of the keys to a well balanced raw diet.
Please don't think I'm being critical here, or trying to put you off raw. I'm trying to help by giving you some pointers towards a better balanced diet for your puppy. There are plenty of pre-prepared minces available from suppliers such as Natural Instinct, Wolftucker and many others. Most of them contain bone and are 80% - 100% meat. Avoid the few that contain more than 20% veggies because their meat content won't be high enough.
Please have a read through this
http://dogsdinner2.webs.com/feedingpuppies.htm and also, if you're on Facebook, join one or two of the raw feeding groups on there to learn more. Rawfeeding Rebels and Raw Feeding UK are good groups to join.
Good luck with whatever you decide, but if you decide to stick with raw please do some more research

and ask questions here and elsewhere.