I use a shorter version with 2.5 gallon kegs and it has drastically improved my hoppy beers like NEIPAs. I don't dry hop in the primary anymore with those beers, just large whirlpool then keg hops. I keg condition too which I think helps with any O2 pickup on transfer.
You will gauge over time how much you can fit in that tube, but I can fit about 3 oz's which is plenty for a 2.5gal beer.
I leave the tube in until I kick the keg and haven't had any issues especially with new wave hops in NEIPAS. My West Coast IPA had a bit of grassiness from the Cascade hops, so I will shy away from that hop in the future for a keg hop.