Runners are not supposed to give lateral support at all - in fact in pure structural terms they should run to the centreline aft as otherwise they twist the mast when in use. Moving them out to the rail allows the mast to twist slightly but means that you can still ease the mainsheet a bit without making sure that there is absolutely nothing stopping the lee runner from preventing the sheet from easing.
If the T26 has in-line spreaders it may be a simple case of being in a situation where one mistake with the runners (ie not having at least one on at all times when gybing downwind) could break the mast. Note that's a "could" - it gets down to the individual boat.
The way you sail is also important. Some boats can be reefed down so that the mainsail head is over the runners and therefore both runners can be left tightened. And many boats that need runners to be in place in a 25kt knot gust from the stern when the boat is hitting head seas, can sail around happily without runners in 15 knots.
If the toe rail is just self tappers it may be a problem to take the runners there, if the rail is through bolted it's probably fine on a 26'er.
While I liked the T26's rig when I mentioned it in an earlier post, if you don't have the experience to assess how dependent the individual boat is on the support of the runners it may be better to look elsewhere. Even things like the tension on the shrouds and the firmness of the mast step and the supports where the mast passes through the deck affects how much fore-and-aft support the mast has.
If you really like the boat then get a quote on fitting forward-angled jumper struts. Boats of similar weight, like Thunderbirds, have in-line shrouds and no runners because the jumper transmits the force of the standing backstay further down the mast without allowing the mast to bend too much. That stops the situation where the runners are not on, the masthead backstay holds the tip of the mast aft, and the mast just over-bends until it snap. See the little upper rigging bits at
external-content.duckduckgo.com/iu/?u=https%3A%2F%2Ftse3.mm.bing.net%2Fth%2Fid%2FOIP.FmhZ11GiHTzAZBrC-c8TcwHaJb%3Fpid%3DApi&f=1&ipt=51129521487cc59cf78d81675acf7e10a0379d70665562371ac449c28f559fed&ipo=images