I bought a small utility ladder some time back for use where I didn't need a 6' stepladder and have now discovered it mostly solves the problem of reaching to the rear of my around the wall layout especially when the level of the tabletop is high. Mine is 44" above the floor. I got it from Home Depot for $50.; http://www.homedepot.com/Tools-Hard...splay?catalogId=10053&langId=-1&storeId=10051 While not cheap, it will come in handy since it elevates me above the layout and allows me to lean across without touching the scenery (at least most of it). Attached is a pic showing what I mean. NO, it's not perfect, I still have to watch anything near the outer edge of the layout, but it's a huge improvement over without it. I am going to see if I can extend the top 'handrail' higher so to give additional clearance over the edge of the tabletop.
Not perfect maybe, but A LOT cheaper than Micro-Mark's alternative: http://www.micromark.com/topside-creeper-step-ladder-support-system,8854.html
I was going to post that, but you beat me too it. That has it's uses, great for a large layout with high mountains and low valleys where you can't reach. Especially for a club. Big problem I see is the size for moving and storage and access in narrow isles. What I like to do is make a 'U' shaped bracket that would extend the top handle/cross bar up another 6" or so to prevent my stomach from hitting the tops of scenery along the edge of the layout.
I would be wary of extending the rail. It might allow you to put too much weight on the front legs and you could go over forward. It should have a designed balance point.
I understand this as I only wanted to extend the top bar 6", not go up another step. It really doesn't change anything since my feet are in the same place and body is the same position. All that would change is protecting the area at the very edge of the table. If anything, it would restrict reaching further.