Microtik queues http downloads help please going crazy

Hi i hope some one can help i have a small wisp and im trying to get my bandwidth to go as far as possible.
at the moment i have this in place to limit other traffic so i can limit encrypted p2p connections. (see below basic script)
What i really want to be able to do is limit htttp downlonds. for example i am giving 3mb connection to my customers and when they do a speed test i want it to show them thay are getting 3mb. but if they download ubuntu from the web http i would like it to start off at normall speed but after a time limit say 2 mins the speed will drop to 100k. I have tryed heavy traffic but the script changes my old one and does not work. Can some one please help its driving me crazy it only needs 4 people to download at once and i have lost 3mb speed.


/ip firewall mangle
add chain=forward action=mark-connection connection-mark=!heavy_traffic_conn
new-connection-mark=all_conn
add chain=forward action=mark-connection connection-bytes=500000-0
connection-mark=all_conn connection-rate=200k-100M
new-connection-mark=heavy_traffic_conn protocol=tcp
add chain=forward action=mark-connection connection-bytes=500000-0
connection-mark=all_conn connection-rate=200k-100M
new-connection-mark=heavy_traffic_conn protocol=udp
add chain=forward action=mark-packet connection-mark=heavy_traffic_conn
new-packet-mark=heavy_traffic passthrough=no
add chain=forward action=mark-packet connection-mark=all_conn
new-packet-mark=other_traffic passthrough=no

/queue tree
add name=upload parent=public max-limit=6M
add name=other_upload parent=upload limit-at=4M max-limit=6M
packet-mark=other_traffic priority=1
add name=heavy_upload parent=upload limit-at=2M max-limit=6M
packet-mark=heavy_traffic priority=8
add name=download parent=local max-limit=6M
add name=other_download parent=download limit-at=4M max-limit=6M
packet-mark=other_traffic priority=1
add name=heavy_download parent=download limit-at=2M max-limit=6M
packet-mark=heavy_traffic priority=8

Use the connection-byte attribute for tcp port 80 and 443, for anything over a specific amount. Then use your packet marks appropriately.

Someone doing a speed test, downloading an ISO, checking hotmail, etc. are all exactly the same thing as far as a router is concerned, downloading a file via HTTP.