Fence panel advice

Jazziboo

Hi
Need advice on fencing please. I need to replace approx 10 6x6 lap fence panels and 2 concrete posts. And need 10 gravel boards. 
The adjacent neighbours garden is badly overgrown with brambles (at least 5ft running the length & width of their garden). 
I've seen some people use two gravel boards height then a shorter panel ontop (still equating to 6ft height).  So with all the overgrowth next door would this be ideal for this situation or would using one gravel board be sufficient?

vw100

If you are using 1ft/12 inch gravel boards then 1 is enough, as two wont look that nice and they are each weigh about 50KG if you buying the normal boards. There are lighter versions available about half the weight but they are 3 times the price of normal ones. I would go for a 1ft gravel board and a 5ft fence.