Saying "we have been made partakers if we hold fast" has the same meaning as "if we hold fast, we have been made partakers". Agree or disagree?
I disagree, because that locks the 'hold' verb into the indicative mood and makes it the action that is completed and sure and ongoing, and puts the verb of being made a partaker in the subjunctive mood of uncertainty, which becomes certain or uncertain based on whether or not the holding fast is the definitely completed action.
The Greek tenses and moods show us that is not the case at all.
Your interpretation puts the 'being made partakers' in the position of the completed action that may or may not last, and the holding fast as the already completed and ongoing action. But the actual Greek tenses and moods puts the being made partakers in the position of the already and completed and ongoing action, and the holding steadfast as the completed action that may or may not continue.
I challenge you to examine closely the truth of what I'm saying. You have the tenses and moods of the two verbs switched so that the holding fast is the indicative, factual, completed action (which the Greek says it is not), and the being made a partaker the completed action that may or may not be true based on the condition of the certainty of holding fast (which the Greek says it is not).
You seem reasonable. I think you are capable of honestly acknowledging what I'm saying.