The drag is the most essential part of a spinning reel. Period. Locking the drag on a spinning reel is actually kind of funny and almost silly. I lock my drag down on my casting reels when I am fishing frogs in heavy pads or jigs when I want to really put an oomph on a fish. Spinning reels are about finesse. Lock your drag down on a 6lb. smallmouth in the St. Lawrence and I can tell you what will happen with that fish LOL...oh wait it will be gone faster than I can explain. Aluminum framed reels are more rigid than others but products like Ci4 and Zaion are better blends of composite that resist flex. I have aluminum and composite framed reels in sizes from 500-3012H and have had no issues with flex. Daiwa's Exist at $800 is Zaion, the Stella at $800 is Magnesium (not aluminum), and some of the best selling spinning reels out there are composite (Stradic Ci4, Tatula LT, etc.). If you are using lower quality reels with cheap graphite and then add no flex braid with a locked down reel and I would then assume a cheap rod with a crummy reel seat since you wouldn't put a cheap reel on a good rod, you may have issues but again, those are extremes. Just like if you take a Honda Civic off road you can expect the frame to flex and maybe even snap.