neutering older rat

as you may know i have been fostering an un-neutered 1.5 year old boy for a little while now. well he's really winning my heart and where he is older and male and of a "plain" variety i'm i little dubious of his adoption chances and was considering adopting him myself. but if i adopt him i have to have him neutered. i do have allerigies to buck greese and so far it hasn't been so bad with only the one male but i do get headaches from him if i have him out with me for any real length of time and i have a bunch of females that i want him to live with and not get them pregnant. but he is older and i was wondering what the risks of that would be. he seems in good health but i noticed when spider and violet had their tumor removals done it took spider (25 months at the time) longer to get over it then it did violet (a little under a year, approx 11months). is a tumor removal any harder on a rat then a neuter or vice versa?

i'd prefer him to be in the big cage with the girls but its not impossible to house him in a decent cage with my neutered male bribery. the headaches are an issue but they aren't disabling, just painful... if neutering would do more harm then good i would keep him in his current arrangements but it would be really nice to not get the headaches and have him loved and doted on by all the girls too.

does anyone have any experience with neutering a older male? are there any thing i should be more concerned about or demand from the vet because he's older? will he be in more pain then a younger rat with the same surgery done? thanks for you help.