I did the same conversion on my 2020 28RKDS. Unfortunately, you must replace the cover to have full coverage of the tanks. I guess if full coverage is not an issue then the cover will go on the 30lbs tanks, just not to the bottom of the tanks. For me, tongue weight was not a consideration because I full time in one location for the most part. Larger tanks save me a few trips to the propane refill station, then it is worth the extra weight. If you want a full 30lbs cover, Amazon has you covered and no need to measure. Amazon lists the tank covers by 30lbs designation. I only found back or white colors, however, I was not looking for any color other than black. Amazon may have other colors, however, that I am not aware of. I hope this helps and is not too late.