Setup and hold time violation constraints for Xilinx Fifo generator

I have a problem concerning the Xilinx Fifo generator and timing contraints described in the fifo manual.

I am using the fifo generator version 9.2 (manual ) to generate a fifo.

I would like to insert the timing constraints which are suggested on page 151:

Add the following constraint to your design – this constraint sets a timing constraint to
the synchronization logic by requiring a ma
ximum set of delays. The maximum delays
used is defined by 2x of the slower clock period.
NET
<fifo_instance>
/xst_fifo_generator/gconvfifo.rf/grf.rf/gntv_or_sync_fifo.gcx.clkx/
wr_pntr_gc<0> MAXDELAY = 12 ns;
NET
<fifo_instance>
/xst_fifo_generator/gconvfifo.rf/grf.rf/gntv_or_sync_fifo.gcx.clkx/
wr_pntr_gc<1> MAXDELAY = 12 ns;
...

If I insert these contraints I get the error:

ERROR:ConstraintSystem:59 
...
REG_CTRL/dev0_daq_fifo/U0/xst_fifo_generator/gconvfifo.rf/grf.rf/gntv_or_sync_fifo.gcx.clkx/
wr_pntr_gc<1>
NET not found

I expected a spelling error, so I searched for this net with PlanAhead, but I could not find a net with this name. I found a primitive which has a similar name ( rd_pntr_gc_9) but no net.

My question is now, what am I doing wrong?
Why are the nets not existing? Which nets could I use instead to apply the constraints.

I am using ISE 14.2 and a ml605 board with a Virtex 6 FPGA.

Thank you and best regards

Simone

tl;dr I want to insert the suggested timing contraints for a fifo from the manual, but I cannot find the nets which are suggested.

p.s. I have seen the answer record AR# 43210, the nets which are described there are also not existing in my design.

Edit: XST option -keep_hierarchy is set to Yes