I say go the whole way and upgrade springs, axles & brakes and toss in a set of Dexter equalizers and wet bolts. If you have LRC tires, I'd also suggest upgrading to LRD tires (expense notwithstanding). Our 29' 6800 lb GVWR TT originally had the typical questionable 2 x 3500 lb axle/spring setup. It's been upgraded to 3" dia. 5200 lb axles with larger dia. brakes and Dexter equalizers & wet bolts along with LRD tires. Also installed shocks.
Now have around 20K miles on the upgrade and has been great - the larger brakes sure work well like when you almost miss a turnoff and need to slow down fast, lol... Going with a complete larger axle/spring/brake package doesn't add comparatively much cost. Al/Ko has an excellent website with detailed axle specs on the various components
here. I thought you could get the larger 12" brakes with 5-lug spacing but don't see it listed on the site. Another thing worth considering sometimes is strengthening the spring hangers by adding gussets above them. A new axle is a pretty straightforward swap and something you could do yourself if you're a DIY type.
