adjustments on trailers. boat

[TTavenier3]

i have a sparten tilt trailer for my 16.5 foot starcraft kingfisher boat. i exteneded the tounge of the trailer because the boat was front was over the ball hitch. i was getting moving around in the boat when the boat was on the trailer and noticed it liked to roll from side to side alot. more than i would expect. so i got out and really looked at the position of the boat. it was perfectly centerd but the rollers are flat rollers not v'd like the boat is. i want to change them to be v rollers so the boat rolls in them straight. but i belive by how close the rollers are to the frame know that i will have to raise the rollers. luckly they are on brackets that can slide up probley slide a good 4-5in up if i wanted. i do want to raise the boat about 2 inches. if i do this will i need to get the wood slides or whatever there called raised to . they dont look like they move so could i just buy taller boards. do i need to reinforce then. the bracket on there know looks kinda weak and flexable to me. or should it be that way.
i currently have 13in tires on there know but i need new ones. there 4 lug. can you buy a new spindle that is 5 lug or are the shank(the hub) different. i have plenty of 5 lug trailer rims and tires so it is more of a convenince to me. but either way will work. any ideas or help would be nice. maybe i should say screw the wood and add those fancy rollers. but i belive i read somewhere thoses rollers are not good on aluminum boats. any ideas. anybody so the swap . any anything would be helpful. thanks