Seems like things are off track and perhaps an examination of equipment and technique might be in order. Otherwise you could keep increasing the dose to a potentially dangerous level when the needle and the technique are not entirely workable.
I can't imagine any good reason to require anything thicker than a 30 ga needle but you must get full penetration into the cavity. That generally takes a 1/2 inch needle length. Some people report success with a shorter needle but most seem to require 1/2 inch. You can feel when the needle breaks through the outer sheath and into the cavity.
You mentioned no stretch. However I always stretch a bit - which helps to obtain a firm grasp and keep good control over the penis during injection. I followed Nelson's thread about trimix use and his advice is sound. If you can massage the penis a bit before and after injection, and preferably get a bit of engorgement prior to injection it aids in accessing the right area and in holding the penis firmly in place during the process.
I hear your frustration and I understand - having also gone through many years of no erections. Hopefully addressing the smoking and weight issues and finding a good workable trimix technique will get you the success you seek.
