I believe this is an aggregate test. So the 25% limitation is based upon the aggregate contributions, and aggregate amounts allocated to the 401(h) account. If your plan allows life insurance, you need to take this into account as well. Take a look at the last paragraph of 415(h), which discusses the aggregate nature of the test.
Caveat - I've never actually SEEN a plan with a 401(h) account...
As for words of wisdom, free advice is worth what you pay for it!