RSTP Alternative - Backup Link Setup

[cloudwireless]

We've been using the AF60LR set to a path cost of 21000 as our primary link with the AF5XHD set to a path cost of 22000 as an alternative successfully on the first wireless hop from the POP for some time.

We now want to add some more identical setups on the next few wireless links in the chain to connect the first relay site to the second relay site however as they will share the same WS as the first alternative link do we need to change the 21000 and 22000 to something else like 20000 and 19000 and so on?

A little help from someone who understands RSTP far better than me would be greatly appreciated.

Current setup
WS-12-250DC at POP has RSTP enabled
AF60LR Main wireless Link to first relay site
AF5XHD Alternative Link (for when it rains) going to first relay site

WS-12-250DC at first relay site has 22000 set as the path cost for AF5XHD and 21000 set at path cost for AF60LR which works very well.