Now I have added two magnets to the bottoms side of the top hull piece. This is for future additions like spot lights or hunter killer missiles.

 As you can see all the turrets have been assembled. They can articulate and with the magnet modification they won't fall off while playing.

 The next step is to cut off a bit of sprue and attach it to the turrets and the Rhino hatch doors.  This is probably the trickiest, but most important part. You need to measure the distance between the floor of the Rhino to the height of it, minus the thickness of the magnets you are using.  I also used a rotary tool to make a space in the floor to accommodate the magnet.  If you are going to do this, be careful not to puncture all the way through the model.
As you can see I have done this with both the Rhino door and the lascannon turret. If you want you can use a few of the Bolters, but I chose not to.

 Once we have all the doors and turrets magnetized, we can make any combination of Rhinos and Razorbacks. Shown here is 5 Rhinos and one Razorback. Below is the configuration I will use to start, 3 of each.

Now the only thing left is the round hatches.