What types/manufacturer boiler insulation is being used and why the selection of what you are using. Who is using the rigid type mineral board and was the rigid board flexible enough to bend around the boiler?
That stuff on the 9010 looks like Kaowool to me.
Calcium Aluminate blankets 48X72 for areas that don't get walked on.
Neither is cheap, but they do a nice job, and if you are careful either can be re-used.
See also http://www.rypn.org/forums/viewtopic.php?f=1&t=30029 which discussed this topic about 8 years ago.
The Illinois Railway Museum has recently done some lagging work on the J. Neils Shay #5, and I believe they used the same "Fibrex 1900 Block Insulation" as was used on Frisco #1630 in the late 2000's. The link I provided there is no longer valid; use http://americanfibrex.com/ instead.
Comes in various thicknesses so you can layer it to get what you want. So effective you can stand on it while setting the safety valves without burning your feet. Held on with wire, and if it has to be removed, just roll it off, then you can reuse it.
Blocks are more trouble and labor intensive than they are worth, IMO.
At the Alberta Railway Museum we have been using Roxul brand stone wool insulation, manufactured by the Rockwool company.
It is available in a variety of thicknesses and lengths, we buy rolls which are then wrapped around the boiler, with additional pieces cut to fill gaps. It is then held in place with wire or metal tie wraps until the rest of the jacketing is installed.
Our locomotive (ex-CN 4-6-0 1392) has undergone her 5-year inspection this winter, and as it happens the new insulation was installed just a few weeks ago.
The rigid rectangular slabs of stone wool were tried during the previous 5-year rebuild, but quickly proved to be a pain as they would not bend or flex like the rolled stuff will.
We use 3-1/2" fiberglass building insulation, without a paper moisture barrier. The jacket is supported by a permanent jacket frame. The fiberglass drains water well, is very cheap, and very easy to apply.
The jacket frame makes for a very smooth jacket as well.
I would suggest that several approaches to nanoinsulation are getting to the point of mainstream practicality -- aerogel, in particular, being something that can be efficiently 'homemade' and then fabricated into panels or some other form that can be applied between boiler and jacketing/cleading.
A different sort might be multiple reflective shield with dry gas inflation between layers.
Good insulation has some interesting implications. The European converted Kriegslok 8055 has very good and carefully arranged boiler insulation, sufficiently good that about 35kW of commercial water-heater capacity (I believe they use circulation past commercial immersion elements) is sufficient to keep the engine not only hot but in steam at nominal pressure indefinitely. This solves most of the issues with both pressure and temperature cycling stresses in boilers, which might even over a comparatively short timeframe justify even substantially higher cost for the better insulation on a working locomotive.