I posted a while back about makePCB, but I have changed my mind about using them I think because of the one time nature of the setup fee at PCBcart.
I know Dave and others have used PCBcart, but I find the quote confusing a bit for a panel given how bad the English is I thought it better to ask here than them directly.
Panel is 6 copies of the same PCB with v-score. The full panel has 468 vias.
They say:
"If need panelized board please select "Board type" as "Panel" and input board dimension as "Panel dimension", if have file for single unit only please panelize it or contact us for panelization before order "
There is no panel dim, just board dim. I select panel and put in my board dim 244 mm x 168 mm.
Different design in panel: I select "1" I presume this is the number of different sub-designs not the number of instances.

? (Is it??)
Route Process: Panel as V-scoring.
Taking the defaults, change surface finish to ENIG.
Holes number: Change to 300-600?? (I assume Vias count as holes and the count is per panel?)
I think everyone else is default except change in color.
I was going to send a "comment" gerber layer to show where to v-score. I backed the v-score 1 mm from the copper plane. Is that enough for the width of a v-score from them?
I apologize for all the questions, but I am poor and this will cost a lot and is my first panel. I would ask them but fear a confusing answer is all I will get due to language.