Yet another piece of info did not have. Either way it couldnt hurt in accomplishing said goal by bumping the dose up a 100mg or so. 3" is alot of mass my friend. 23" is pro size, in fact, bigger than most.

I don't do site injections any more but what I would do is slightly heat my gear under the faucet and draw with a slin pin. I would then procede to inject .5ccs in each head of the tri repeat eod or e3d. I really don't recommend doing it though. For me your best chance would be to up your dose another 500mg and increase your calories typically you'll need to put on atleast 8lbs of bw usaully 15+ in most cases. With your arms as big as they are now I am going to assume you have excellent genetics for arms. So in the rest of your cycle try adding calories daily until you see steady weight gain on the scale. So you're looking to need to gain a minimum of 24lbs to reach your goal. Hope this helps. Good luck!

Well reading your original posting like you said, seems like alot of people would laugh. I'll be honest it put a smile on my face as well. If you already have 20"+ arms you should already have your training down.
Even at 15%bf that is a fucking huge arm @5'8" tall. Are you looking for advice on your dosage adding something else that might compliment what you're currently taking? Personally I don't see you putting 3" on your arms that quickly even by stuffing yourself with 10kal a day. You're taking a gram of test? Like I stated originally your only hope is to try localized growth from site injections. I don't know you personally so its hard to give a concrete statement that could really help you with your goal. With the limited info I've read, I can only conclude that it is outside the relm of possibility here.