Growth Hormone is a better option. Running T3 while using slin is somewhat counterproductive (unless youre already on GH which has been shown to suppress t3 levels). 25mcg is not much more than a replacement dose either. Using a supraphysiological dose of T3 tends to increase protien degradation at a higher rate than it increases the rate of protien synthesis.
In my personal opinion, insulin is a great tool, that should really only be used while bulking and to break through platues short term. I am not suggesting my opinion on the matter is gospel as I know many others will disagree. One last comment. If youre using insulin, be ok with gaining a little fat. Get those calories in and grow.