So the most I ever got on deadlifts was doing sumo style and I got 405 for just one rep. I trained and trained and still kept coming back to 405 for one rep. So, I decided to switch it up and do sumo romanian deadlifts. Well, to pout it simply, I have flat feet and I'm in my early 30s. I just want to either make it to 405 for a set of 3, or the equivalent to 405 for a set of 3, which I believe would be 335 for a set of 8 on the sumo romanian deadlifts, starting with the first rep off the floor. Anyway, last week I did 335 and could only do 1 rep before I dropped the bar, this week I was able to do barely 3 reps than my right hand couldn't take the weight. I have no pain, or issues with my back, or anything. It is simply my grip. I am doing double overhand, but with grip gloves. Double overhand feels more comfortable than mixed grip. Any advise? I've been so close to my goal many times, yet can't seem to reach it.