You should be alright but make sure you keep a close tab on your blood pressure and heart rate! Ritalin is mildly potent dopamine reuptake inhibtor. High testosterone levels may lead to a slightly higher level of endogenous dopamine, so there is a slight chance of overstimulation. Try starting out at half your normal dosage just to get a feel of the two drugs effects.
Also be sure to take them only with meals. This is becuase methyphenidate is thought have a slightly higher bioavailability when taken with food (more drug gets in your bloodstream). And also dopaminergics tend to take a chunk outta your appetite, so this way you can still make sure to get enough calories. Also if it does lay a beating on your appetite, don't force a meal - you'll get nauseous. Protein shakes will probably help alot since they aren't as filling as a meal.