Also you might want to tweak your settings with these steps:
1) Install a network stumbler in order to see your signal strenght.
2) Review the signal strength of both your routers on serveral spots in your house by walking around (write the data down)
3) Than tweak your broadcasting strength in your modem to make sure there is a reasonable gap in signal strength on the desired hand over points in you house (Wireless >> Profesional >> Tx power adjustment / make sure you adjust the 2.5 and the 5Ghz channel !). This is important as you need a reasonable difference in signal strength at the hand over sport in order to make a Mesh network work. Your bigest challenge is to adjust the transmission power in order to make sure that the area your modes are covering are overlapping but not so much that the handover space is as big as your house resulting in no handover at all. This is important as wifi is a two way street. Your modem can be broadcasting until the end of your street, your ipad is whispering back and therefore you still have a bad connection. So in a mesh network it is quality over signal strength.
4) Review the signal strength of both your routers to make sure there is a reasonable difference in DB at the desired hand over spots (at least 5 DB difference is my advice)
5) At the hand over spot lowest signal strenght you can now set your Roaming assistant to roam at a value at the lowest signal strenght (Wireless >> Profesional >> Roaming assistant / make sure you adjust the 2.5 and the 5Ghz channel !)
6) Make one more walk with your network stumbler to check if the handover is done correctly at the desired spots in your house
7) Continue tweaking (it took me about 6 runs to get it spot on) by looking at your modems log and network stumbler results while walking around the house.