The slokas 5-35-50 and 51 are very controversial. In sloka 50 Hanuman describes to Sita that Rama killed Vali in combat. And supplements it in sloka 51 by saying “after killing Vali by means of his strength”. This could be because the occasion did not warrant any more details. But the statement using strength (tarasaa) needs a more clear explanation. The word ‘tarasaa’ can also mean efficacy(capacity for producing a desired result or effect)/effective. So is this a subtle way of saying trickery? I think Hanuman thought, the occasion does not demand more elaboration than this. That is why he called a good Diplomat.But it is anybodies call.
All Sloka Translations are from the site Valmiki Ramayana