Just had a jl 500/1 installed with 2 jbl single 4ohm 15' subs running at 2ohm, when the Advd Bass Cntl is turned on i get a very slight bit of feedback through the subs, does not get worse with volume

SOURCE: 2ohm vs. 4ohm

The 4 ohm has more wire. The more wire wraps you have in your voice coil produce more ohms. The Voice coils move up and down based on Current flow through the Coils. You get higher current flow with 2 ohms, but you need a hefty AMP to drive it. Also 2 ohm Speakers are easy to add up without exceeding the 8 ohm limit of most AMPS.

SOURCE: 500/1 v2 and one kicker VS12L7

It will work fine. This amp is stable to 1.5 Ohms, but is designed to put out about the same amount of power at 2 or 4 Ohms (unique).

SOURCE: 4ohm subwoofer and 2ohm amp

just run str8 pos and negative

SOURCE: Can i wire 3 jbl gto1204d subs into 1 jl audio 500/1 amp

You can connect them in a series/parallel configuration. Put two of them in series and then connect the last one in parallel across the two in series. This would give you an impeadance of around 2.7 ohms. Only do this if your amp is stable at 3 ohms or less. I am not familiar with the specs of your amp. If your amp is only 4 ohm stable you can not do this.
This would also give you half the power on the two subs in series as the power for the one that is parallel. The two in series would be sharing the total output signal, where-as the one in parallel would get the entire output signal from the amp.
if you were to connect a fourth sub woofer in this configuration it could give you a 4 ohm load, by adding the fourth sub in series with the single sub that is in parallel. or in other words, yu have two sets of 2 sub woofers each in series. That gives you two 8 ohm loads (two 4 ohm subs in series is 8 ohms). Then you take the two sets of subs and parallel them (two 8 ohm loads in parallel equals 4 ohms).

If i had a picture to show you it would make sense, two subs in series that are in parallel with two subs in series.

SOURCE: how to wire a crossfire vr602 2 channel amp at 4ohm and 2ohm

I would be more worried about the amp than the speakers, those subs should handle the watts with no problem. The problem will be in the amps ability to remain working with a bridged 2 ohm load. It may not even stay on without going into protect mode with a 2 ohm load. If it does stay on then it may get really hot and shut off from the heat off of the Mosfett Transistors, or it could burn the Mosfetts from driving them too hard. Basically it's your choice, run your amp hard and gain more volume or run it with slightly less sound and have a cleaner sounding more stable amp that will stay on and have less chance of being damaged. If it's not loud enough the best thing to do is buy a different amp that better suits your needs and fits the application. In your case a 2 ohm stable Mono amp is going to be your best bet or a 4 channel amp bridged into 2 channels and run with 4 ohms on each channel. Or another exact matching amp like your 2 channel amp bridge them both and have each powering 1 of your 4 ohm subs. I used two VR mono amps to power my two 12" 4 ohm subs for a few years