The s parameter files of HMC370 and HMC369 are same. Even though the file names are different the content is the same that of HMC369. Can you please upload the actual S parameters file of HMC370
You're right. Unfortunately these were taken quite awhile ago and all we have. These multipliers are intended to be used in the same manner as a gain block. Drop it in to your 50 ohm system and use it as is. Attempts to improve the match at either the input or the output may degrade the multiplier functionality as the inter-stage nodes are not available to the user so it's impossible to provide a simultaneous conjugate match.