Archer C6 v2 - Use whole flash

Hello. I have a TP-Link Archer C6 router. It works very well on openwrt, however by default it can only use 4MB flash. The EU version has 8MB flash. I've read that you have to use mtd_concat to connect dual partitions(?) Sadly this is too much for me and I would really be thankful if someone could make firmware that utilizes whole 8MB. This router doesn't have a USB port so extroot is not an option ;/