Mods to record player advice

Setting up second listening room, got harman kardon pm645 amplifier and wharfedale diamond 230 speakers with Yamaha streamer, my dealer is getting a rega rp1 as a trade and said I could get for 300 cdn,comes with the carbon cartridge but I've got a grado silver I can throw on it.Im a machinist and have a p3 always had the itch to modify but it sounds great already, anyway now I've got the rp1 I can play with,its got antiskate which is great,I want to build some sort of vta adjustment and make a new platter,my question is what material would be best for platter,I was thinking aluminum or acrylic with the same bracing as the p3,any suggestions or feedback would be appreciated.