Sean, I don't think you have problem in casting less than 90' 9/10 GS with T&T10150-5. As you already figured out, you are able to make long cast-100+, with under-rated line for a rod ( for example, line 8/9 for a rod 9/10/11) but not with over-rated line for a rod. With line GS/ XLT, your final goal is to handle the 95' whole head- lift and sweep to D loop, which may requires a lot of practice. When I choose midspey or GS/XLT line weight for a rod, I do single spey with the whole head out ( in your case 95' out)- when I lift and sweep to D loop without feeling too heavy, I know the rod is suitabe for the line.Maybe, T&T10150-5 is better with 8/9 GS if you want to cast 110+. Last year, I fished with 8/9 XLT and GLX 9140-3. I found making a long cast with double spey with ease but not with single ,especially with weighted fly. I don't know why you want to fish with XLT line. I will tell you my feeling about this line. XLT is designed to cast longer distant, for fast swing, for shorter leaders, for smaller flies/dry flies, for longer rods ( preferably 15'+) and lastly to make you better spey caster- this line is just perfect for summer-run steelhead or atlantics, but bad for the other seasons.