Good for you! It's a blast shooting the old "workhorses" isn't it? Had so much fun shooting those types of guns.
One thing I wouldn't fall into though. Just because you see a lot of people shooting fancy custom rifles off of fancy one piece rests...don't think they all started out that way. Most started just as you are doing.
The thing to remember is that any of the high end guns factory rifles like the 52D's/E's, 40x's, Anschutz 54's can compete with about anything out there. Where the difference comes into play is consistency. Hence, the migration to custom actions, barrels, etc by those who want to go a step further. But you can do very well with the older factory rifles.
I started with a 40x, 52D and Anschutz 2007. Shot both aperture sights and with scopes. First BR formal BR match I ever went to, I pulled the apertures off the Anschutz, stuck on a scope and went to the IR 50 Nationals. Didn't win, but did pretty well. Have won a few targets here and there with all of those guns in formal matches, and even won a couple of matches when things fell in line. The funniest thing that ever happened was once I stuck a tuner on a Kimber 82G to see if it might help my aperture shooting and while trying to tune the thing (had a scope on it) ended up winning a BR match! Talk about funny! A $400 rifle beating nothing but custom guns!
The moral of the story is you don't need a custom rest or a custom rifle to do well. You've figured that part out. But, and this is a big but, you do need stuff like that when you want to go further up the food chain. Just the nature of things.
As to shooting apertures, I've used the Palmas, Olympic and International sights on some of my guns. Also different Anschutz aperture sights. But the best I've had the pleasure of using is a Phoenix rear with some of the Euro accessories. Takes things to another level. But I mostly shoot apertures at 100 yards now. At 50 I do pretty decent, but at 100 it's another world and it's a blast when you drop them all in the x ring. Try it sometime. The best feeling in the world is shooting a 200/20x on an A5 at 100 with aperture sights. Better than winning any big BR match I've ever won...
I've got some buddies just like you. They shoot off of bipods only, factory rifles, no tuners, and they even stand while shooting. Though, they do have a bench they sit their rifles on while shooting. Went down there one evening to shoot with them. They shoot all kinds of targets, money is involved and they will take your lunch money if you don't know what you're doing. Well, even if you know what you're doing they will take it! Heck after we shot a few different types of targets with scopes, we started shooting apertures with the A23/5 at 50. It was the best time I've ever had in shooting a match. And I've shot in quite a few matches!
Good luck going forward. All of this is fun. Just don't think that someone needs a fancy rest or a fancy gun to be good at something. Just enjoy what you're doing and don't make it into something it's not. I've still got my Kimber 82G, and if I stuck a scope on it, I would not be afraid to shoot it in any BR match on this planet. But it's too much fun shooting apertures so I just do that anymore. Got burned out with all the stupid side shows going on in BR so took a step back and just shoot for myself anymore.
Do try a bipod though. You might find it's even better than shooting from a two piece rest. Just takes a few minutes to figure out how your gun likes to be shot when there's no rest involved.
JMO
Kenny