The 9" auger will fit on the planter drill head, the same as a PT 24" auger. About 6 weeks ago I took delivery of a PT2425 with the trailer package which came with the planter drill head. It automatically came with the 9" auger and I switched out the 18" auger for a 24" auger - a size I use in my business. The trailer package also included (obviously) the trailer, a spare tire for the 2425 and the trailer, a tool kit, extra tie-down strap, a drain hose, extra filter, a 3 ft. trencher, stump grinder, 30" forks, 48" boom pole, 48" rototiller, 10 cu. ft. light duty bucket, 5 cu. ft. heavy duty bucket (got it with teeth), and then the above mentioned augers and drill head. I also got the 4 cu. ft. cement mixer and had it mounted on the trailer right away. A couple weeks ago, I had my dad weld up a 24" extension for the 24" auger so I can drill holes 54" deep, which worked great the first time I used it.
I've been very busy lately and I'll try to get an update with all the various projects I've been doing in another thread in the future. It may not be until the end of August as I don't see any slack time before then.
Hope this helps !