sflow sampling for qfx5100 virtual chassis for junos space

hi gents,

     did anyone try configuring a virtual chassis qfx5100 devices for sflow towards a junos space log collector?

     heres my sampling rate .. any thoughts?

set protocols sflow polling-interval 20
set protocols sflow sample-rate ingress 2048
set protocols sflow sample-rate egress 2048
set protocols sflow collector 1.1.1.1 udp-port 5000
set protocols sflow collector 2.2.2.2 udp-port 5000

my junos space doesnt collect such sflows. im thinkin about some settings on the junos space.

thanks