That seems like a pretty good rate. Excess tubing is not going to cause a lack of flow if it is at the same head and going down in elevation. Only problem is a risk of kinking. Tom lifters are rated a 3gph max at zero head pressure so you could use a measured container to see the rate. ie One gallon in 20 minutes. Just lifting out of a bucket, say 10", you might be down to 1.5-2 gph though.