30 minutes is a while to inject before eating and it is not something I would normally do. If I had a high BG (maybe 220+) and was planning a meal I may take my bolus (carb ratio and sensitivity) 30 minutes prior to a meal. I would be concerned of going hypo before the meal and before the meal hits my bloodstream just like you.
20 minutes before a meal seams more likely. If my BG was a little elevated (160+), I wanted to eat a lot of carbs, and the glycemic load of the meal is high. I think this may be a trial and error type of experiment that you have to conduct to see at what point you go hypo and at what point you PP 1 hour and 2 hour tests stay the lowest.
I like to bolus maybe 10-12 minutes before any meal of 45ish carbs or more (if my BG can handle it).
30 minutes before a meal sounds like the old humulin R or Regular talk, but I guess it all depends on how fast your insulin starts acting on the carbs.
I use the combo bolus (dual wave for MM) with some meals. In general I will use them when I am eating a high fat meal (pizza) or high protein (steak). Or I will try a dual wave when I have eaten the meal before and see my BG start to slowly wander up 3 or more hours after the meal (eating out). I suggest you look at some of the postings in TAG (Total Available Glucose - TAG) Group. That group will go into much more detail than I will and a bit of it is trial and error to figure out how you specifically digest things.
The basic concept is that about 40-60% of protein you eat can be converted into carbs and about 10% of fat can be. This conversion takes longer and therefore can raise your BG later than expected and slow the digestion of the carbs you eat. For me (through trial and error) I have found that taking 65-70% of the bolus (not including correction) up front and taking the wave for the remaining 30-35% of about 0.6 to 0.8 units per half hour (or 1.5 units per hour).
Things to be aware of: You probably have the protein and fat somewhat factored into your meals I:C ratio. Therefore if you are going to count all your carbs, protein, and fat you may overbolus (bolus what makes sense to you). From the bit I have read, diabetic's digestion varies a bit and my numbers may NOT be useful for you (but may be a starting point). It stinks when you are expecting a meal to digest slowly and dual wave bolus for it, then the meal hits your blood stream fast and all at once. You will get a bunch of Insulin on board with a rising BG that you can do little to correct. If you are eating a meal that you know (from experience) will cause your BG to rise at 3+ hours, they why not give it a try?