Question : Setting up MSTP on HP procurve Ring Topology how to set priority and path cost

Ok i am trying to set up 2 separate "redundant rings" in an HP procurve environment. originally the site was going to use complete star topology but because the Fiber was pulled and chained that wasnt possible and they did not want to purchase new equipment..  the "Core switch is an HP 4208vl with Fiber GBIC modules".. each of the other switches in the rings are HP 2610_24 switches running R_11_22 software.. there are 18 VLANs in use...  101-115,30, 50, 999 are the ID's
All VLANs exist in the Core switch (4208)..  VLANs 30, 50, 999 are shared amongst the two rings.. meaning they belong to both. one ring consists of VLANs 101-107,30,50,999 and the other ring is VLANs 108-115,30,50,999...

the way this works is there are 7 buildings in the first ring... each building a separate VLAN..  however all VLANs for that ring belong on all switches of that ring...

physically we connect like this...B1,B2 etc designates building number
Note there is only ONE core switch I just noted it at oth "ends" to show you its a ring...
in the () are GBIC port numbers on the core switch
Core(a1)---B1--B5--B9--B13--B12--B8--B4--Core(c1)
Core(d1)---B3--B7--B11--B15--B14--B10--B6--B2--Core(e1)

as you can see 2 rings currently im just trying to get ONE ring working right before trying to get the second physically wires... so I set my Core 4208 switch at priority 0 so he remains root all the time... if Core goes down the network is defunct..(not my choice but customer wont buy more equipment)
so on ring 1 theoretically id Like to see uplink from B13 to B9 to be forwarding and the uplink from B13 to B12 to be blocking... which sometimes it does....
so that way traffic to Building 1 goes out of Port a1 on the core.. traffic to B4 or B8 goes out of port c1 on the core..  However what I get are MANY topology changes.. 200-300 a day resulting in a mess.. packet loss. etc.. whereas if I disconnect one of the core ports and disable spanning-tree the integrity is SOLID without any packet loss...

so I am sure im missing something here.. im not understanding how to set path-cost etc.. as im not sure in HP how to define a "PATH" in my MIND path cost from core port a1 to B1 would be "0" and from core a1 to B4 would be huge.. as id rather the path be c1 to B4...and vice versa.. so my questions are:

1] for 2 rings do I need to set up MST regions?
2] how do I define a "path" and then set its cost?(B1-B5) or (B1-B8) ,etc
3] how do I avoid continuous topology changes... things should only change if a link "breaks"
4] since this is all HP is there something else I should be using?
5] should I set all other ports other than the Uplinks in each switch to an admin edge port?

sorry im really new to setting up STP snd MSTP..
-Christopher

Answer : Setting up MSTP on HP procurve Ring Topology how to set priority and path cost

If I understand STP the way I think I do (and beleive me, I may not understand it), costs are cumulative back to the root of the bridge.  So you have to add all of the costs to the "right" and then add all of the costs to the "left" of B13.  The complete path back to core with the lowest cost should be the path that is taken.