Solo Mining on a private test net

I want to explore peercoin core. I am trying to set up a private 2 or 3 nodes peercoin network just for exploration.
I have compiled source code and disabled internal peers.
I have also re-mined an updated genesis block with updated nTime.
I am also able to connect two clients running in a virtual box vms.

Now i want to start a miner similar to that internal miner in older versions. I have lower the difficulty so cpu can easily mine a block in 2 or 3 minutes. I have tried BFG Miner, CG Miner, Easy miner and ntgbtminer (https://github.com/vsergeev/ntgbtminer). But didn’t succeed.

I was unable to connect BFG, CG and Easyminer with my local node and initiate mining.
ntgbtminer was able to connect to node and start mining but throw an error during submission of block to network.

when i try to manually submit the encoded block produced by ntgbtminer via peercoin-cli, it throw error saying Invalid Coinbase transaction.

Can anyone help please…