There will be two models of the Valiant one with and one without Warp Nacelles. The reference images of these type warp engines are very low resolution so I will be filling in the gaps with my own creativity.
There seems to be an interesting history associated with the engines from the Jein model. From these early images we can see the engines as there first were on the model.
It then seems that the pylons were repositioned, however this could have been the original angle of the pylons and it was changed to match the hull. I'm not sure the orders in which these photos were taken.
The engines were then removed and put on the C1-21(aka Mystery Ship) model.
Then the pylons were again repositioned so the the engines are straight across from each other.
Then when the C1-21 was used as a prop in an episode of Voyager the engines were removed.
I wonder what happened to them. If anybody sees a stray pair of Warp Nacelles...
Actually I plan on incorporating the changing pylon angle into my design. My idea is that early warp ship had these movable pylons so that they could better tune the warp field by moving the engines themselves.
Here is my start on the warp engines:
Just testing the glow for the reactor domes.
View from the opposite side.