Okay, I have a proven track record of mishandling and misunderstanding how size increase works with spell and I am also a sucker for punishment, so here I go...
The same mage as the author of Jail made of Leather wants to made his cloak into his talisman and wants to invest several effects to survive in the North.
From Cloak to Yurt
Turn a cloak into a Yurt.
Mu(Re)An, Base 2 (major change, yet preserve the substance), R:Per (only the cloak), T: Ind, D: Conc. The +1 Rego requisit is to hold the yurt without requiring poles.
I need to toss in a few size modifiers, and here is my math: assuming a cloak around 3 square meters, a first size increase will multiply its mass by ten, or every dimension by 2.2. Since the tent does not need to be thicker, the surface will increase from 3 sm to 30 sm (length and width by 2.2, and the extra mass not used for extra thickness bring another 2.2 factor, which ends up exactly to be 10) , and a second magnitude increase will bring it to 300 sm.
Is this part correct or do I miss another factor somewhere ?
Assuming it is okay, let's keep going.
For a yurt of roughly 50 sm (the size for a lab, for example), assuming a cylinder, 3m high, with tops and bottom, it needs roughly 140 sm, more than enough.
To be comfortable and considering further expansion, let's had a +1 for complexity and +1 for flexibility, that allows to create a more complex structure with a few connected smaller yurts (bedroom, reception hall) since there is some spare square meters of leather.
As such, it is a rather thin wall yurt, not the traditional robust construction, and it won't keep much heat in.
So I want to add a CrIg spell to generate lights and heat (CrIg Base 4). D: Conc, T: Touch (with the new clarification being discuss Per cannot affect anymore a container, am I right ?), R: Room.
R: Room to select individually light and heat in each room created by the spell.
As a cloak, if my mage wants to stay warm, could he used this effect with R:Room, despite not really being a Room (closed cloak could be loosely considered as an enclosed space, so kind of fit the descriptor, but if it opens it is no more a close space.
Finally, I want to add a Ward against Gale Wind (ReAu Base 10). Can I use R: Per, T:Ind with +2 size modifier to protect me (while a cloak) or the yurt compound (once transformed), which is a magnitude-friendly option? Or should I use R: Touch (+1), T:Structure (+3) (because of two or three rooms), which is two magnitudes higher than the first option ?