David,
I also have a TC-30 with R-1 or Ag tires and know how tippy it can be even on realitivly mild slopes. Spacers are the simplest way to go and probably only on the rears. They will induce a bit more stress on the rear axle bearings, but nothing like the stress on you and machine if you roll it over!!
I would suggest 3" to 4" wide per side in aluminum or steel, your choice. I would also fill the rear tires with suitable solution (most any tractor dealer or tire shop that deals with tractor tires should be able to advise on this).
NH specifically advises against mounting the front tires to wide setting probably due to excessive stress on wheel bearings and/or spindles with a FEL. I am not sure you would gain much by reversing or fluid filling the fronts, but you certainly could if you want.
The primary reason to go to duals is for additional floatation, which I do not gather you need. They will certainly also help with stability. If you elect to go this route, you can use one size smaller diameter for the outer tires which will help keep your steering as easy as normal while the outer duals would still provide the extra stability when at extreem angles.
I also do not recall what tires you are running now, but R-4 Industrial or turf are wider overall than the R-1 AG and also hold more fluid fill. Useing a solution such as Rim Guard or calsium chloride will add about 11 lbs/gallon. Go with typical 75% fill.
My feeling is that if you can not get comfortable with 8" wider rear wheel track (based on 4" spacers) and fluid filled Industrial or turf tires, you probably should look at other types of tractor. I bought a Power Trac 1845 specifically for the REAL steep terrain on my property (20, 25, 30 degrees plus). There are other possibilities as well.
Good Luck... and wear that seat belt!