Bunch of arrow questions

[La. bowhunter]

I was recently at a sporting goods store that was going out of business and ran across a heck of a deal on some Gold Tip Extreme Hunter 55/75's. So I buy a couple of dozen just to give them a try. Well after a couple of days of tuning work I almost didnt make it. With the standard insert and a 150 gr. point I almost ran out of arrow before they were stiff enough to tune. Well the real problem is now my finished arrow weight is only 420 grains and from my 56 pound bow that only comes out to 7.4 GPP. Is it possible get another 100 to 150 grains of arrow weight without affecting the spine of the arrow without spending a bunch of money.
Thanks in advance for your help.

[J. Adams]

have you tried weight tubes?  3-Rivers sells them in 3gpi, 5gpi and 8gpi.  I've heard some guys use weedeater line with good results.

[Matty]

What length did you have to cut them to what length can you go down to?  Brass inserts are the way to go  I cant believe you had to cut them down that much to get them to fly right unless you have a very LONG draw..

[Mo. Huntin]

I know you can add lots of weight with weedeater string I think it affected my arrow tune a little though.  People put rope in their also.  I wondered what would happen if I filled one with calking, that would probably be way to heavy.  I know when I put weed eater string in mine I took a little back out because I lost more trajectory than I wanted.  good luck.

[La. bowhunter]

Matty they are now 30 1/4 inches long which gives me about an inch hanging out the front so brass inserts are out of the question. I have a 28 1/2 inch draw and dont feel comfortable with my broadheads coming too close to the riser.
Mo. Huntin I will have to give the weedeater string a try to see if I can get what I want should be a lot cheaper than weight tubes.
Thanks guys.