I have a few that are deep, too. The only "easy" tool is a real Peavey TR wrench. Had the fortune to acquire a couple of good ones over the past few years.
What does the Peavey TR wrench look like mech? This is the TR wrench that I got with my Foundation is this a Peavey wrench, or an aftermarket tool? The only markings on it is 5/16th.