Bill Roberts - "Besides the simple chemical hydrolysis described above, the esters can be removed by enzymes in the blood called
esterases, though water still is required for the reaction. The great majority of hydrolysis occurs with the help of these enzymes or by non-specific reactions with proteins. These reaction cannot take place while the esterified steroid is dissolved in fat. Thus, while the esterified steroids are dissolved in fat, they are protected from hydrolyis, and thus serve as a depot for the drug, giving extended duration of action."
You have to get it so the oil is deep enough in the muscle to stay put and help preserve the esters. If you start to get a spill outside the muscle's "storage space" - the esters then can become compromised... leading to a miscalculated release of the parent hormone...
If you have really low body fat than a 5/8 might work but I would recommend sliding the skin to the side during administration - and then releasing it only after the pin is removed. This can help the pin go a little deeper - and also prevent bleeding by sliding the skin over the site...