Need advice on corney kegs

[needmoremaples]

Last year I stored my unfiltered syrup in new plastic 5 gallon jugs bought at the maple store. This year I want to try the corney kegs. Do they seal good normally? Do I need to modify them to hold a vac instead of a pressure? I just like the ability to store in stainless and cleaning should be easier. Picked up 3used for 75 bucks locally

[maple flats]

Years ago I converted a bunch of Corney Kegs to store syrup. Based on my experience I suggest you weld a flat plate over the oval top opening. Before that, cut out an opening the right size to weld a 1.5 or 2" sanitary over the hole and remove the spring loaded blow off (vent) and weld it shut. Then use a 1.5" or 2" sanitary plug , silicone seal and clamp. If you can't weld SS find a good welder who can.
My method was much cruder and failed about 10-15% of the time. I made a way to push the top down tighter, but some O ring gaskets still leaked. I even tried one year filling the kegs with hot syrup, then I pumped food grade nitrogen in to 35 psi using the original closure. Some still failed. I see welding as the best method. This is where I buy my sanitary fittings and adapters https://www.brewershardware.com/Sanitary-Fittings/

[needmoremaples]

Will the current smaller knobs leak when vacuum is applied? I'm a steamfitter so I know some good SS welders.