Only way it could possibly be safe would be to increase the processing time substantially. You'd have to compute the correlation between the excessive amount of air in the jar and the processing time needed to remove it - if that were possible to do. But it ain't. ;) So now you have jars that must be refrigerated and consumed ASAP because bacteria is free to grow in them. From the NCHFP FAQs on canning: Do I really need to leave a certain amount of headspace in the jar? Yes, leaving the specified amount of headspace in a jar is important to assure a vacuum seal. If too little headspace is allowed the food may expand and bubble out when air is being forced out from under the lid during processing. The bubbling food may leave a deposit on the rim of the jar or the seal of the lid and prevent the jar from sealing properly. If too much headspace is allowed, the food at the top is likely to discolor. Also, the jar may not seal properly because there will not be enough processing time to drive all the air out of the jar. Dave

my opinion is that maybe the plum tomatoes pickle better than the regular toms because they have less juice inside. Anyway I like to pickle with plum toms. I pick them slightly small and none are really big toms. but if I slice a few in half top to bottom then I can get a few extra into the jars. I also like to use more vinegar in my brines. In fact I have always used all vinegar and no water. that makes for a very sour pickle that I like and it is also more safe because the pH is always low this way. So one thing to remember. You can always use more vinegar and less water. It simply makes for a more sour pickle. I like them this way. if you do use water. the water is important. you really want very soft water. hard water can cause a problem getting the pH low.

I still have the lime here (Mrs. Wages brand) and it did help to hold the cukes a bit firmer for the all vinegar sour pickles. I do not use alum anymore and because it still seems to be linked to aluminium and allzheimers I was not going to even try going any further with it. The lime was used, and the whole cukes were soaked in it for 24 hours in the fridge. I used huge stainless steel bowls that take up a whole shelf in the fridge. I cut off the tips of both ends prior to the soaking, They did get a long rinse afterwards, but even for that, there was a bit of white sediment in the brine after a few days. I also used a bit of tumeric for some color. They were quite pungent. I could have even added a bit of my acid blend and made them even more potent.. My sours are not fermented. They are just 100% plain white distilled vinegar, salt, and a little tumeric. My pickled pepperoncini are also done that way, but without the tumeric. My half sours are just a salt brine with a dash of vinegar added after they sit on the counter overnight. Ive also use the pickling lime for making some sweet mixed, but it was just for the cukes to soak in first. The amount of alum used in a 7 quart batch of sour pickles was something like about 2-3 teaspoons for the toatl amount of vinegar brine. With Pickle Crisp, you do have as slight flavor of chlorine, but that tends to dissipate once they are opened and allowed to 'breath' a few minutes before serving. A chilled pickle always seems to be a bit crunchier than at room temp. FYI> Rumford brand baking powder has no alum in it. Baking soda is basically bicarbonate of soda and nothing else. There is also a bakers ammonia that is still used today for some Swedish cookies and pasteries. I can't taste Pickle Crisp, but that might be because of the heat of the peppers, or the strength of the flavors and spices I use in regular pickles. Mrs. Wages and Ball mixes are the primary ingredients I use when making spiced pickles, and I add extra spices like dill, celery seeds, mustard seeds and such to the various kinds of pickles.There is nothing worse (besides a sour or mushy cuke) than a bland tasting pickle. A recent America Test Kitchen episode dealt with making a flaky pastery for a big berry tart. They mixed the butter and flour to a very course mix, then used their palms to press the flour into the butter lumps. This helped to spread the butter into thinner bits. Ever made puff pastry? I have, with excellent results. MUCH better than the Pepperidge Farm frozen stuff. It does take a long time, a cold work surface, lots of patience and lots of rolling between each chilling.

Agree that you'll want to increase the acidity for safety purposes. Since they are larger than pearl onions you will have a density problem and that can affect safety. You can cut/pare them down to size and pack them very loosely in the jars so there is plenty of brine - do not pack tightly. I'd eliminate all the water from the recipe and do them in straight vinegar. Dave